Error of tax return total file size of attachments

Hello, I'd tried to submit tax return, but it keeps telling me the following error: 5014 Your submission has not been accepted. The total file size of the attachment(s) must not exceed the maximum size limit of 5mb. Please check. But my total file size of attachments is only 3.5mb. I had 20 files and all are pdf files. What can I do? Thanks a lot. Merry X'mas, Kin

I remove 1 attachment of loss shares disposal which can be reported next year. Then re-calculate all the data and finally successfully submitted the tax return! The attachment file limit is actually 19 not 20! And for the final further attachment section, if I choose no, then all the capital gains attachments will be deleted and need to upload again! The tax return system has these 2 bugs. I don't know why it can exist without fixing! Thank you very much for not replying over 20 days. I finish this final battle by myself 2 weeks before deadline. Thank you very much!