I am not sure if this is an actual issue, all auditors that looked at this so far haven’t mentioned this being a problem. But I will have to investigate what the exact state is.
(Looks like the IncludeSec folks did a decent job in 2019. Hi Eric!)
However, I misread this: I thought the padding was being done on the cleartext signing side, but this is padding of the signature itself. So there's some malleability here, but it isn't susceptible to DO'1985. I'll update my top-level comment.