Hey there, this is because of an integral flaw in the RC300, it is not meant to be master or slave to anything other than another RC300…
The RC300 doesn’t automatically do what the Aeros does, where it re-syncs to the playback of the BeatBuddy consistently to ensure there is no drifting. Even by setting the tempos to the same place, the BeatBuddy doesn’t communicate with the RC300 with much results.
There may be a fix to this issue, check out this post