The pics really help. Your white layer has what I would call, crystalline cracks. That is more of a word to call it then what caused it. I have seen this before, some a finer pattern and some a larger pattern. It comes with age from sun UV damage.
This back area with the bubbles, still has some unanswered things about it. This pics helps for sure show what you are against.
I can also see that your caulking is all deteriorated that can be seen in the pictures. Those cracks in the caulking also come from age and sun UV damage.
To your comment about the rubber roof feeling loose from much support under it from when you got the camper, is accurate. The Sunline rubber roof structure is unique to them. I am not sure they are the only ones in the RV industry who made them that way, but if there are others, the list is not many.
This older post of mine tells some on how the Sunline roof structure is made.http://www.sunlineclub.com/forums/f6...ture-8925.html
The 0.040" rubber membrane is bonded to a thick dense corrugate board. It was call "budboard" by the folks at Sunline. I believe that is more of a nick name then the actual brand name or material. Some call it cardboard, but in the technical world, cardboard is made different like a cardboard box with flutes between the layers. This budboard is solid dense structure. Think of the backing of a 8 1/2" x 11" note paper pad. The back sheet is dense. Just in the case of budoard, it is a lot thicker. By hand, you cannot rip bubboard very easy if at all. It is very strong in rip resistance.
Once they bonded the roof structure, it was pulled over the roof rafters spaced every approx 16" centers as one piece. The budboard was rigidly supported at the rafters and just spanned between them with no added support in many places. So, it feels loose between the rafters. There is no way it can support high point loads like a person's foot standing on it. But it can take a snow load as the weight is not concentrated in one spot.
Here is a picture of a 2004 Sunline roof being rolled up and off the roof during a camper restoration. This will give you a better look as to why the loose lack of support feeling is normal on a Sunline rubber roof. This camper has a lot of water damage at the back wall.
The whole roof structure off on the ground
Some of the rafters with the insulation lifted up
Here are my thoughts on your roof.
First I would want to better understand the bubbles. There are "normally" a few ways bubbles come.
1. There was a defect in the glue when the roof was made. Bubbles may not show up until maybe 2 to 3 years later. In this case, no water was involved.
2. When a water infection occurs, and the most common way a water infection occurs is through leaking sealants in the roof system. This can range from a rusted out screw in a gutter rail wicking in water, to caulking failures anywhere on the roof. Yes, a mechanical hole from a tree limb etc is possible, but you can see that easier.
The water can seep in the sealant leak and then wick and spread across the budboard. Over time, the budboard deteriorates from the bottom up. Water and rotting corrugate then can attack the glue to the rubber. In most cases, the budboard just totally deteroites and falls away from the rubber leaving no support.
3. Some other way yet to be learned on how roof bubbles form.
Try this with the bubbles, it may help shed some light on if you have a water infection. The bubble seems to bounce back up as you stated. But can you press the bubble down below the normal roof surface? And does it feel as stiff as the rest of the roof or does it feel rubbery and very little support under the bubble? Like a tire tube rubber feel. I am assuming these bubbles were not on your roof back in 2001? Yes/no? Any idea when they showed up and did they ever grow in size?
To help confirm a water infection, a moisture meter for $40 can help a lot. See here http://www.sunlineclub.com/forums/f7...per-17613.html
You can scan the inside ceiling and walls. And in some cases, you can scan down from the top of the rubber. The roof will give false readings if a fungus is present all over the entire roof. The meter will read the fungus. But if there is no fungus and other areas of the roof scan 0% moisture, then if you get higher readings over the bubble areas etc. it helps confirm a water infection. A water infection in a ceiling or wall, will not always show up inside the living space. It it very common to have 0 signs of water infection in the living space, but have a very wet behind the wall board.
If you find out you have a water infection, then you need to decide if you want to fix it and how long you want to keep the camper.
If by chance you have no water infection, and you want to keep the camper, then a roof repair is possible. I would suggest this,
1. Clean and then demold the roof. This is a bleaching process after the laundry detergent cleaning.
2. Replace all caulking. Take up all the old and put new fresh caulk down. This will seal up the sealant bad areas.
3. Do an Eternabond treatment on all roof seams. Must wait 1 month from fresh caulking to gas off and you can do this in segments over time.
4. Once the E bond is completed, pending the time span, another demolding treatment may be needed. Then apply a roof coating to rebuild the white layer.
5. Once all is done, start a 303 aerospace UV treatment over everything rubber or vinyl on the roof on a periodic basis.
I am recommending to fix the actual sealant issues first, then do a roof coating. Using a roof coating to fix bad sealants is not a long term fix. The coatings are too thin to fix the sealant foundation issues.
I can explain more into the "how to" do all this. And if you really want to keep the camper, as an alternative is to put a new rubber roof on. It will cost more, but it will last longer and you can repair any water damage.
Hope this helps