Full disclosure: I’m not a TCL user.
As a test you could disconnect BEAM 2 from the TV to see if there is any kind of odd interaction over the HDMI cable. SONOS does not send any IR commands, but it can receive IR commands if you have set this up with the TCL remote. Usually, Volume commands are sent over the HDMI cable to BEAM as the TV receives Volume commands from its remote. This is usually an automatic pairing when the HDMI connection is established between TV and SONOS. If the TV is not capable of this, you can usually configure the TV remote to send IR Volume commands, then train BEAM 2 to respond to these commands.
Maybe rebooting the TV will help.
I don’t much see the purpose in using infrared here. If I’m not mistaken, the TCL TV (voice) ‘remotes’ are often BT/RF linked to the TV.
If that is correct, then I would perhaps use CEC on the TV itself to control the volume of the connected Beam over its ARC/eARC port connection.