I've a pair of pretty new bibshorts that came out of the wash with some glued joints no longer glued. It's where the pad is contained within a "pocket" which is glued closed BTW.
Washing instructions are 30 deg which I *think* was followed but it appears possibly not.
What glue could be used to get these back up and running?
Sewing machine?
Took mine to a local shoe repairer, was lucky enough to have a common interest in ice hockey, and he glued them for free. Still holding strong a year later.
This happened on a pair of Altura progel bibs I had. Got them refunded under warranty.
IMHO these are joined by heat rather than glue. If you use glue you need to be careful that you don't get hard, dried glue where you really don't want it 🙂
I'd have them sewn with a fine thread inside the indented line, and make sure that the gel pads (if fitted) are still in there and not in the bottom of the washer 😳
On two of my bib shorts where the pad sewing has come undone (the pads were sewn in, not glued) I took them to a local tailor - a different one each time. Each time the tailor said they didn't have whatever special sewing machine is used on lycra, but they would give it a try - and the repairs seem to work.
TLDR: Try your local tailor/seamstress
You could try Mcnett Goretex Repair Patches. Less than a tenner.
I've used these on cycling shorts in the past, and the patch holds on well.
It's a soft flexible bit of iron on material (almost like a bigger inner tube patch), I think you could use one overlapping the edges to reseal the pad.