I have a Stomp XL and BeatBuddy 2 and I can’t replicate your issue.
From ChatGPT, here’s some additional things to try: ChatGPT - Stop MIDI Commands HX Stomp
You can refine the question and run the query again as well as addressing the follow-on questions.
If you ever sort it out, let us know how you did it.
Edit: I tested this again this morning and it did not work. 
I’m leaving this here in case anyone has the same issue; they can see what I’ve tried.
TL;DR: I think I fixed it. I had the Helix midi base set to channel 2, and the BB2 midi in set to “Any (OMNI)” after changing that to channel 2, I have not experienced the problem any more.
Well I think I may have finally figured it out; thanks in part to your suggestion. I used the chat gpt prompt you started and fine tuned it to my issue and the helix floor.
It took me through all of the previous suggestions (I had queried chat gpt before coming to this forum) and I had already changed all of the settings it suggested e.g. setting midi pc change in global settings off, changing midi in settings on the Beatbuddy, ensuring there were no lightning commands. It seemed there was no hope, but then it suggested I mismatch the helix base midi channel and the Beatbuddy midi in channel just to suss out where the PC change was coming from.
I noticed that I had the BB2 midi in channel set to “Any (OMNI)”. I had read earlier that I could either set it to the exact channel or to the “Any” setting and either would work. Since I’ve been experimenting with lots of gear in different orders as both master and slave, I left it on “Any”. However, after matching the helix base midi channel and the BB2 midi in channel to #2, I have not been able to reproduce the problem.
I’m getting tired, so I’ll try again tomorrow when I have more time to experiment, but it seems this has fixed the issue, which would be amazing!
Thank you! I was about to give up. Never-the-less, I persisted. 
I’ve exhausted all possibilities and this is what I found out from Chat GPT:
Ah — now we’re at the heart of it. Thanks for the clarification. Let’s summarize where we are:
Global PC Send = OFF
Snapshot PC Send = OFF
MIDI Clock = OFF
MIDI Thru = OFF
No Command Center instant commands
No loops, only DIN Out to BeatBuddy
Removing all CC assignments stops the BeatBuddy from triggering
But leaving any MIDI CC assignments (for normal control) causes the BeatBuddy to start playing when changing presets
At this point, what you are experiencing is just a firmware/hardware behavior of the HX Stomp XL:
HX Stomp XL always sends the first MIDI CC value on preset load for any assigned footswitch, even with PC send off and no instant commands.
This is how it “initializes” the state of all CCs when you load a preset.
BeatBuddy reacts to that CC (probably whatever CC you’re using to Start/Stop), so it begins playing automatically.
The unfortunate truthThis is not configurable in the HX Stomp XL firmware.
The “preset load initialization of CC values” is baked into the design.
That’s why all the usual fixes (PC off, Command Center off, snapshot off, clock off, MIDI Thru off) cannot stop it.
In short:
There is no way to fully prevent the HX Stomp XL from sending at least one CC on preset change if you have footswitches assigned to MIDI CC.
This is why many people run into the “BeatBuddy starts playing” problem — it’s a known limitation of HX Stomp firmware.
I’m returning to this post to state that I’m now having the same issue with my Helix and the Aeros. Changing presets on the Helix is triggering the Aeros to mute the selected track when I have the helix set up as a midi controller for the Aeros. It only happens on presets that have midi commands assigned. So I think that pretty much confirms it’s a Helix issue.