Looking @ the pic I can see that the plastic sheet is
Coroplast
It isn't the most durable mat'l. I know when exposed to sunlight for long periods it gets brittle. We've used them for no trespassing signs, & after a couple of years, they've had it.
I don't know if being in a shade spot will reduce this problem or not. If it was me, I'd replace the panel w/ a more durable mat'l, sheet plastic or aluminum.