Yes it could be a missing signature, though i do see 2 signatures after decoding.

The other possibility is it could also mean the wrong signature (see https://bitcoin.stackexchange.com/questions/58176/what-does-16-mandatory-script-verify-flag-failed-non-canonical-der-signature)

Have you double checked the signing functionality/logic to ensure you're using the correct address in the chain?

Dexx any other thoughts?