model result plddt array missing residuals

Hi
Im running alphafold2 and getting (as expected) model_result for each of the models. when i open the pkl file most of the sequence i run has all the input, but there are few proteins with missing values in the plddt array.
for those proteins the array contains something like that - [34.8213755 , 33.35643787, 33.83871669, ..., 35.53027995, 31.07384778, 29.75013154]
I thought maybe its only a display problem but it seems to be the real output in the file.
i looked for a documentation but couldn't find any relate issues
any idea why it can happen?

Thanks!