Thanks for reporting this issue, it has not been entirely fixed, but shooting a grounded disc against a grounded cube/wall should not result in this behaviour anymore, there was an issue where ricochet could trigger under false circumstances when pushing a grounded disc under another grounded object. This behaviour might still show up every now and then on a grounded Ball, given the nature of the ricochet mechanic and the Balls shape.

I've noticed this with grounded ball instead of cube as well. Doesn't count it as a head on collision, but does slow down the disc and maybe even force it into the ground a little more.