Suddenly baked lightmap causes LAGS on Android platform

I have 2 small gamelevels with ~10mb baked light data. I also have 3 with only realtime lightning.
Platform: Android

The issue: When scene with baked lights loads, it lags as hell for 30sec-1 min. Slideshow. Then some parts of the level (which has baked lightning on it) become absolutely white with a few artifacts. Then everything works fine except that white look of some parts.

If I load scene only with realtime lights, no lags at all.

Additional info:

  • Tested with both lightmappers (Enlighten & Progressive). Same problem.
  • tested on 3 android devices (so it’s not device specific problem).
  • tested with Unity 2018.3.9, 2018.4.14f1 LTS, 2019.2.15f1
  • Generate lightmap UV’s on meshes is on.
  • If I create totally new unity project with the quite same meshes, the problem do not reproduce. There is a lag too, but it lasts 1-5 sec. and then dissapears with no harm.

What else:
I noticed that it has something to do with light data loading or so, because the scene becomes a bit brighter when lags gone. Not sure btw, hard to notice. But it looks like Unity tries to load something, fails, lags, then finally loads with broken parts.

What can I do with it? How to solve it? Any help?

Could you please submit a bug report with the above-mentioned information and with a small repro project, if possible? Thanks!