I can confirm that everything correctly works using the integration you linked.
I still think it depends on the home assistant core modbus implementations as both the core and the integration uses the same library pymodbus 3.1.3
Have to check but I think the library uses asynchronous client while core use the synchronous one.
I am also looking into a solution to update the two variables:
- sensor.idm_warmepumpe_aktueller_pv_uberschuss
- sensor.idm_warmepumpe_aktueller_pv_produktion