I have an older quarter dome as well, and experienced the same thing. I was able to lay it out in the sun which fixed most of this, I think I may have sprayed it with a garden hose in the backyard.
After which I sprayed it down with a can of waterproofing from walmart. I took it out of storage for a backpacking trip to iceland last summer (2019).
the tent is heavier than my others, but extremely durable, so it got the 'nod' to travel.
here's some pix of it in action.