Hard to tell from your brief description.

I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.

I did that and sonos said there’s nothing wrong with the system itself. The diagnostic came back with no errors 

That suggests that the issue is somewhere upstream, so that the audio being sent by the TV isn’t reaching the Sonos. There’s not much we can do about that in this forum. 

Couple of random thoughts, though. Fist, I’d make sure that the software on both the TV and the FireStick are up to date. Older software can sometimes cause problems. 

You’d also want to be sure to lock down the application for both Disney Plus and HBO Max to Dolby Digital, as well as the FireStick itself, to not allow them to attempt to send a Dolby Digital Plus signal, which currently the Beam can’t interpret. 

Everything is up to date. Everything is set to DD, not Plus. All other apps work fine and don’t have issues. 

What TV make/model is it? - does it have a pass-through option for its Digital Sound Out? - Some TV’s have this option through its ports, but if it is set to Auto, some TV’s, like TCL for example (some models only) may (try to) process the Dolby audio and interrupt it. If the TV has pass-through then select that option in its audio/sound Settings.

Samsung. No pass-through option. 

I’d double check with Samsung or Amazon, then. If Sonos has confirmed that the issue isn’t on their side of things, it likely is indeed an upstream issue. Which could include perhaps the FireStick’s connection to your network, as a random guess.  

Apparently (I read) some Samsung TV models may achieve better audio pass-through when the optical Port is used for the connection to a Receiver - so that might be worth a try, using the Optical to HDMI adapter connection to the Beam. You will lose the HDMI-CEC control of the TV, but that ‘may’ possibly help your audio issue. It’s worth a try, nothing ventured etc…

Otherwise you may want to consider the option of using an audio extractor/splitter to bypass the TV ports altogether instead.  

Didn’t check with Samsung. But Amazon said it’s nothing on their side either. Again I only have these issues with Disney+ and HBO Max

Certainly suggests it’s not the Sonos, either, if it works with everything else. There must be something unique about those two streams.