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.

DSC02145 - reduced.jpgDSC02346 - reduced.jpgDSC02347 - reduced.jpgDSC02348 - reduced.jpgDSC02392 - reduced.jpgDSC02416 - reduced.jpgDSC02429 - reduced.jpg

https://youtu.be/YkOgDHadfjQ

https://youtu.be/mIjs3VGcFho

REI Member Since 1979 YouTube.com/philreedshikes
Iceland's Laugavegur Trail (Hotsprings Trail) from Landmannalaugar to Thorsmork 1-5 July 2019. Backpacking
Backpacking Icelands famous Laugavegur Trail, from Landmannalaugar to Thorsmork. July 1-5, 2019