Did you get this issue resolved? I have the same problem

Problem with certifying document/pdf. Running lc es 4 sp1, linux in cluster. Works with jnp://xxxx:1099 but this error is shown when i try to sign with jnp://xxxx:1100. Everything seems fine with the cluster-configuration. ALC-DSS-300-003 Insufficient SIGNATURE_FILLIN permissions in the input PDF ...

I agree, even with support its impossible to get the quick-fix...