When I first got my Deepeeka seggie, I had all of the shoulder plate straps stretch out, fray and break within 2 months of use.
Now after a few years the girdle/belly plate straps are starting to fall apart.
The leather, as you can tell, is poor quality, and those rivets and rivet plates/washers are tin or aluminum - way soft and pretty easy to remove.
For a temporary fix, I used strips/ties of leather to tie the plates together - I looped one end of the string around the rivetplate (inside where it meets the plate), and tied it to the "broken" strap, careful to tie it so the plate was in the right position/spacing within the others. I ended up with little bits of string and ties on nearly every single strap!
You could also just loop the string around an entire plate, and tie it to another, but the strap will show...But it is secure for a temporary fix.
The best thing to do is to re-rivet all of the [shoulder] plates with better leather and better rivets. Check leg xx's site
www.larp.com/legioxx
re-doing the shoulder straps solves a number of problems - you have the chance to cut down the shoulder plates to a smaller, correct size, and also be able to better size it to your body.
You'd be replacing it with proper, stronger leather which will last you much longer.
the process isn't all that difficult. It just takes a little time, patience and some thinking/planning ahead. If I remember I think I spread out the work on my shoulder plates over the course of 2 weeks, an hour or 2 each nite or so. And it's surprisingly easy. My hardest part was cutting down the plates from 3" wide to 2" wide. The plates are of inconsistent thickness/gauge, so that's what took me the longest. Riveting was pretty quick.
I recommend getting copper roofing nails, should be available at any hardware store. Look for 1/4 diameter flat heads. I think standard size is 1 inch long shanks, but when you cut them down, you can save that shank and use it as a rivet for belts, or even other parts of the seggie! (then you don't need to buy other rivets)
Also get yourself some brass sheet stock - You should be able to find suppliers online or at hobby shops - get yourself a few sheets of 18 gauge brass. Draw a grid of ca. 1/4" or larger squares, grab a drill with a 1/8" bit, and drill holes in the middle of the squares and cut out the squares with tin snips...Now you have a bunch of rivet plates/washers. You'll use them both in the seggie and for belts....and other uses!
You'll only really need washers for the big shoulder plates, and the 4 back/scapular plates on the back of the armor.
also - always a good idea to have a small bag of leather ties and lacing for such emergencies. they are extremely useful.