IOG advises SPOs running their pools (both relay and bp nodes) to downgrade to 1.34.1. The versions tagged with 1.35.0 and 1.35.1 have bugs, and thus the upgrade before the Vasil hardfork should be performed with a newer version. Until this newer version is ready, pools should continue to use 1.34.1. The upgrade to the final version should be performed from 1.34.1.
Here is a video explaining the problem with version 1.35.0 on mainnet: