Periodic error when scanning a block
Hi guys! 

During transaction search, the following error occurs sometimes in Openmonero logs:
`2019-02-22 09:20:36,397 [W,OM,OutputInputIdentification.cpp:xmreg::OutputInputIdentification::OutputInputIdentification(const cryptonote::address_parse_info*, const secret_key*, const cryptonote::transaction*, const crypto::hash&, bool):37] Cant get derived key for tx: ...  pub_tx_key: ....`

Could this lead to the fact that some transactions are skipped and don't get into MySQL?
Hope you guys could help me to understand and fix it.