Siren going off at night randomly (after service)

so I dropped my car off at the dealer a few days ago for a brake fluid flush (that’s it).. I get the car back and do my rideshare driving for hours.. get back home around 11:30pm and 2 hours later the siren is going off by itself in garage..

I go into garage and check things out and hit the siren button on my remote to shut it off.. I was standing around for about 5 minutes until I left and as I left garage , it went off again by itself.. so I unplugged negative terminal on battery so I could sleep..

Long story short, even after alarm is reset after unplugging the battery several times over night , it’s still reoccuring..

I just left the car at the dealer for 4 hours so they could see if problem happened again but it didn’t..

I do want to note that I just drove the car 10 minutes to the dealer and not several hours ( problem did not reoccur )..

So my question is, what could this be?

My plan is to keep battery untouched tonight when I get home and if siren goes off tonight again, I will drive car early tomorrow morning for a few hours and bring it to dealer around 1pm and let it sit for a few hours to see if it reoccurs.

 

I know it seems ridiculous for the electronics to act up after a brake fluid flush..kind of like blaming the tire shop for engine issues.. but it was weird how it started same night as repair..

Well at least problem didn’t reoccur last night after leaving battery hooked up..

Hopefully doesnt return..wonder what it was..service advisor at my dealership was saying he’s never seen that..

 

I just put in a brand new Optima yellowtop a few weeks ago... no issues with electronics since then, except this (in fact I think my car runs better with Optima) ..but not sure if it’s battery..