Montage mode issue

[tigerA]

Runing zoneminder in Firefox on client.
In montage mode CPU load 30%, network - 20% from 1Gb.
On screen have some still image and don't have any reaction.
What's hapeened?

[tigerA]

Montage mode work in this case.
Option - WEB_H_VIDEO_MAXFPS is decreased to 3 on any chanel wide.