When a blank disc is in the disc drive, ImgBurn will show in the right hand side some "Disc Information"
including "Supported Write Speeds: ".
I'm not sure if this accurately takes into account the CD speeds, CD burner speeds, or both.
So far, 4x burn speeds for CD-Rs work for me (no idea about 1x or 2x).
To get a 4x burn speed, you could try using an external CD/DVD drive, computer or laptop
that might be older and have that lower speed available (or you could ask a friend with an older PC to try burning it on theirs).
And manually set it to 4x in ImgBurn.
Another idea is to try using higher quality CD-Rs.
But you (might) still waste a disc
because my guess is the bigger problem is the burn speed is a too high
or your specific CD burner is somehow less compatible for PS1 CD burning.
Apparently compatibility issues are more common in newer CD burners.
Someone claimed higher quality discs work fine for them even with higher speeds/max burn speed, but I can't confirm this myself.
In ImgBurn, check that the "verify" checkbox is ticked when burning a disc, if you don't have it set that way already.
Some people recommend enabling OPC in ImgBurn,
I think you do that by going to Tools > Settings... > "Write" tab > enable "Perform OPC Before Write".
For some reason I didn't have this enabled myself, maybe I've just been lucky,
or maybe it's unnecessary for some CD burners.
Just in case, you may also want to verify your game backup .BIN and .CUE files using a game database.
I'm not sure how to do this myself, guessing it involves checking game file hashes
on websites like redump .org?
Or compare your copy with someone else's (online or from a friend who knows their copy is perfect)
by using free software for comparing MD5 or SHA-1, etc. file hashes.
If the file hashes match, then they are identical.
In FreePSXBoot Unirom, you can try running games natively or in a different mode (NTSC/PAL), see if it makes any difference.
