Is changing frequently the mood of a scene a bad practice?

[磯七ラスミ]

Having some relaxing tea party, then a tornado arrives and while everyone is panicking, the playful girl of the crew is having fun. That makes everyone relax while still spinning in the air. One of the party members feels nostalgic and start crying, having some flashbacks about his/her childhood and then... you get the idea.
There're ways of pulling it out successfully? May readers still take it seriously or it only works for comical purposes? I want to read your thoughts on this.

[Gear]

I'd need to see more examples to potentially think otherwise, but that sounds like, best-case scenario, it'd be perceived as comical mood whiplash. If it's handled oddly or poorly, it'll probably just be confusing.

[磯七ラスミ]

I'd need to see more examples to potentially think otherwise, but that sounds like, best-case scenario, it'd be perceived as comical mood whiplash. If it's handled oddly or poorly, it'll probably just be confusing.

Hitting the mark! Mood whiplash is what I'm talking about.
You have some characters trapped and tied that are very scared, then one of them speaks out a sad observation that makes the two very sad, even pour a couple of tears. Soon a monster, pet of their captor comes in the room and they change their mood to starting hopeless screams.

[Gear]

Not sure if that particular example qualifies as the mood changing or mood whiplash. You're describing fear, despair, then despair and fear. The two emotions are commonly linked in fiction, so no, I don't think in this case it would cause that. If the trapped characters suddenly started singing Baby Shark, that would be mood whiplash.

[Katy133]

I'd recommend watching Bob Larbey's work (particularly the television series As Time Goes By and Mulberry) and studying the dialogue in them. These series are able to switch between comedy and heartfelt moments in a very natural way. Bob Larbey is one of if not my favourite screenwriter ever, and his work has definitely influenced my writing.

[PeterKmiecik]

From pure description You've provided - yeah it kinda sounds like jumbo thing. But.. execution is key. I'd be rather carefull though, wage Your ability to pull this off.
Maybe try to focus on 3 changes, give them purpose/context and I'd also try to reflect on connection of all three. Cause and effect