I had this issues for several weeks now and finally found the solution on a reddit forum, i share it here in case someone still needs it
I had the same symptom. PS3 games run well but when i launch a PS2 format game, i got 3 beeps and red light.
It was because of my 4K TV which isn't recognized...
@K3Nv2 I got some cheapies at wallys, that are pretty good, already have lost a few expensive ones (one falls out and gone, can't find) while cutting grass so bought some cheap ones, and of course never lose these cheap ones. (Cheap meaning only $35, compared to air buds which I only have 1 of 2 now)