"It looks like the game is trying to spot in the default player orientation from the vehicle, not where the player's camera is actually pointing." – that is a very good description of the issue and should help the developers reproduce it and hopefully identify the root cause soon.
I was able to reproduce this consistently. After entering a vehicle, spotting works when the target is located directly ahead of the player's default orientation in the vehicle, even if the camera is looking elsewhere. This suggests that spotting is using the player's default orientation rather than the current camera direction.
Some whining (not relevant to the issue/solution):
Teamplay in vehicles is a major feature of the franchise. Not being able to spot while in vehicles makes effective teamwork significantly more difficult. Unfortunately, the latest patch (1.4.1.5) that was rolled out to production did not address the issue. 😒
I wonder what introduced this bug, or rather why this system needed to be changed in the first place, because spotting worked almost flawlessly before the Season 4 update. My gut feeling is that it might be related to the boats. 😅