I had the same problem as a lot of others, worked sometimes for a bit, then stopped.
I’m not a python guy, I spent way to many hours with chatgpt reworking the code. Mine seems to work well now, I have had it running a couple of days with two bm6’s and they don’t seem to be missing any packets. I’m doing 59 and 61 seconds for update rates.
I also added a counter with two automations, they reset it once an hour so I can quickly see if it’s doing ok.
My fork is here if you want to try it, I won’t be able to help if there are any issues. (ask chatgpt 
)GitHub - bsrotten/BM6: Home Assistant integration for Battery Monitor BM6
The automations:
alias: BM6 - increment success counter
description: ""
triggers:
- event_type: bm6_success
trigger: event
actions:
- target:
entity_id: counter.bm6_success_hour
action: counter.increment
mode: queued
alias: BM6 - reset hourly success counter
description: ""
triggers:
- minutes: "0"
trigger: time_pattern
actions:
- target:
entity_id: counter.bm6_success_hour
action: counter.reset
mode: single