Busco string_type error

I am trying to run BUSCO on a protein fasta file generated from a gff3 annotation, which has worked without a hitch in the past. This time, no matter what I do and regardless of the fact that I am using the exact same tool parameters, I receive the following error:

"1 validation error for toolshed.g2.bx.psu.edu/repos/iuc/busco/busco/5.8.0+galaxy2 (request model)\ntest\n  Input should be a valid string [type=string_type, input_value=None, input_type=NoneType]\n    For further information visit https://errors.pydantic.dev/2.13/v/string_type"

Thoughts on what may be causing it and how to fix it?