I suspected a bug with bushes and their camo values lowering drastically upon moving the tank in or behind them, went to test it. Whole thing:
Tank 1: Ru 251, 473m viewrange, 31.1% camo (BiA, 3 crew members on 100% camo skill, 1 member on ~70%, does not have camo paintjob).
Tank 2: WZ-132, 465m viewrange, 33.9% camo (BiA, 100% camo skill on all 4 crew members, has camo paintjob).
Note that a light tank has the same camo value when moving and being stationary. So it should not matter if the tank moves when concealed.
Tank 1 spots Tank 2 on 328m if no bushes are in play.
Tank 2 spots Tank 1 on 334m if no bushes are in play.
Tank 2 spots Tank 1 on 127m if Tank 2 moves towards a stationary Tank 1 concealed by a bush that is transparent to Tank 1.
Tank 2 spots Tank 1 on 321m if Tank 1 is concealed by a bush that is transparent to Tank 1, with Tank 1 moving barely at all (literally pressing W/A/S/D for 0.1s).
Tank 2 does not spot Tank 1 on 321m (or way less, didn't write down numbers) if Tank 1 is concealed by a bush that is not transparent to Tank 1, and moves a little.
This was tested on different maps with different bushes. The described bug also seemed to apply to medium tanks, so it is not a LT-only thing. Different light tanks were also used, so it is not limited to specific tanks either.
It seems like since 9.16, bushes only give a tiny bit of the camo they used to give to a moving tank behind/in it, if the bush is "transparent" to the tank.
Both replays: http://wotreplays.eu/site/3003904#steppes-slartibartfart-sp_hpanzer_ru_251 http://wotreplays.com/site/3003890#steppes-thegaminglion-wz-132
Here something similar in video form: https://youtu.be/znmLfYKpKt0?t=3m30s This is from a different testing game than described above though, but still displays the issue well. The Ru 251 is stationary and unspotted, with a wide enough layer of bush in front of it to prevent any spotting other than through the bush itself. As the tank moves even just a tiny bit, it gets spotted immediately although the camo value the bush gives the tank should not change.
If you skip to 4:10, you can see that it requires the spotting WZ-132 to move 170m (from 300m to 130m) closer in order for the stationary Ru 251 to be spotted.
Also tried to recreate the situation on http://www.wotinfo.net/de/camo-calculator with this result: http://i.imgur.com/KbZ9Nhx.png - the resulting numbers differ slightly from what I perceived, but are almost identical.
Though, once one adds the bush density, it doesn't parse anymore.
In general it would also make sense to decrease the Sixth Sense delay by a second, since on average it probably takes about 1s less to get spotted, considering all distances.
Anyway, I hope what I tried to describe is clear enough and gets fixed/clarified soon.