Need help with some steempy code concerning voting

Hello my fellow steemians,

I wrote a few lines of code to help me do some automated voting. I use the steempy libraries with visual studio code.
So far my code works well but I recognized that once in a while the working code stops to do what he should. I would guess it is roughly oe out of ten votes. I could not find a mistake or a correlated problem with the post I wanted to voted for.

The error message is:

13 N5boost16exception_detail10clone_implINS0_19error_info_injectorISt12out_of_rangeEEEE: unknown key
unknown key:
{"author":"rahulsingh25843","permlink":"bsnl-launched-four-new-broadband-plan","what":"unknown key"}
th_a database.cpp:385 get_comment

{"call.method":"call","call.params":["database_api","get_active_votes",["rahulsingh25843","bsnl-launched-four-new-broadband-plan"]]}
th_a  websocket_api.cpp:124 on_message

I found a lot correlated to this error on the web. But most of this relates to eos. The only one link I found was from @nosajj. Luckily for him he only had a lettering error which I can exclude in my case because most of the time the code works.

I cannot quantify but it feel like the problem got worse during the last days!
Please can anyone help me!

Kind Regards