About 8 years ago, I was offered some Sharpe 190w PV panels that were seconds.
I chose and tested and got 17off.
While at the manufacturers/assemblers, they recommended that any repairs to the rear film or lead out box, as mostly all had some slight damage, that I use specifically only this stuff, and not just any ordinary silicone.
The panels have been excellent ever since, and the mastic stays and does the job.
Pics.
The special mastic.
Rear of the panels showing the scratches all covered, I couldn't get white colour.
I even re-sealed the front glass edge, it works well as we have a new eco system growing, haha.