I shot videos in vertical orientation with DJI Pocket 2 (holding OP2 horizontally) strangely some videos on desktop show vertically & some (wrongly) as horizontal. Seems when I tilt down it goofs up the orintation so How does Pocket 2 sense the orientation?
So in future I take care & get all my vertical videos to show up vertically.

We're you in Follow mode or FPV? My understanding is Follow keeps the horizon level while FPV tilts as the gimbal is tilted. Think a quick test will confirm the appropriate setting.

As an aside to this, I find vertical videos displayed on horizontal screens disturbing / confusing when published with opaque replicated side views used to fill up the horizontal screen.

The video's orientation (vertical or horizontal ) is determined by the gimbal position when starting recording.

some reference:

Marty Markoe Posted at 3-23 03:36
We're you in Follow mode or FPV? My understanding is Follow keeps the horizon level while FPV tilts as the gimbal is tilted. Think a quick test will confirm the appropriate setting.

As an aside to this, I find vertical videos displayed on horizontal screens disturbing / confusing when published with opaque replicated side views used to fill up the horizontal screen.

Yes I was shooting in Follow mode, I will test it with FPV mode if that solves the problem.
Update:
FPV mode - tilts as I tilt in vertical mode (I should have used this mode)
Follow mode - tilts but limits the tilt to approx 15-20° not more than that. (Seems that limit caused the problem in my case)
Tilt Lock mode - locks the tilt in vertical mode keeping vertical as vertical

Ranjan Posted at 2021-3-23 05:14
Yes I was shooting in Follow mode, I will test it with FPV mode if that solves the problem.
Update:
FPV mode - tilts as I tilt in vertical mode (I should have used this mode)

Hi , For taking vertical pics or videos , do I need to follow the FPV mode ?