Have you tried the instructions on page 30 of the user manual?

Some of my earbuds can re-pair with a hard reset, but I’ve never tried to do it with mixing 2 pairs of the same buds…

IMO I would not try and repair those, unless you are very comfortable with electronics, plastics and understand the batteries. They typically have 1-2 Li-Ion cells under the part that hangs behind your ear. Ruining the sealing on those could lead to sweat ingress and eventually short circuit during use.