Reflection Strange Behavior

[PetrT]

Refliction gone when PGI cache is on
notice reflection of door molding
and figure with hat

[PetrT]

it must be so?.Or must to correct some shader params or render setting

[Dade]

it must be so?

PGI is biased so it can "cut stuff". If you want a more accurate floor reflection, you can increase the "path.photongi.indirect.usagethresholdscale" (from the default 8.0) to use more often brute force over the PGI cache (and improve reflections). Try to use a 2x/4x/etc. values. Or You can altogether disable PGI cache on the floor.

Or must to correct some shader params or render setting

Check if the variance clamping value is too low, it usually explain differences when using env. cache (does the scene has an env. light ? I have a vague memory of a large area light but not of an HDR light ).

[B.Y.O.B.]

(does the scene has an env. light ? I have a vague memory of a large area light but not of an HDR light ).

It uses a sky light if I remember correctly.

[PetrT]

works as needed