The autobetting on Primedice has been flawed since the start this is a known fact.
Started with not stopping on loss when it was set, rolling 5-7 times after the bot had been stopped, now the issue you pointed out.
The autobet on PD is flawed it is as simple as that. Is it caused by lag or too many users, maybe but the fact still remains, the autobet has issues.
Duplicate the result and I will heavily reward you, I'm 100% confident in auto-bet. There's seemingly no way that a 0.05 input would place a 0.5 bet unless the user accidentally put in that amount. We have a large sample size of 20M rolls per day, majority from auto-bet which have been completely issue free. If what OP is claiming is true it means that there is a massive fundamental flaw in our bet logic.
I will give it a shot and see if i can replicate the issues.
P.S I have sent support emails about it and so have others that i know from PD. Not lately tho as i havent had much time to play.