Thanks for the answer, Grant.
I have tried to tamper with Zorro.mt4 code
I've uncommented `Comment("Runs ",count," Loops ",loops); `
And seems like it's ever growing and never stops. So the problem was with the main loop.
I have made `uint loops = 0` non static and added loops limit in a single run ` while(cmd != 0 && loops < 500) `.
Now it works ok - MT4 is responsive and prices are updated.
But I'm still seeing Loops 1..2/Loops 500 blinking (a screencast is here
https://drive.google.com/file/d/1XbQCqY3A8jYroq1Xq1p_2Dt3ljzZ8voW/view?usp=sharing)
So I assume Zorro sends too many unnecessary messages to the bridge.
Same problem with Z1 or TradeTest.
UPD: The code of the command which spams the channel cmd=170 (CMD_ASSET)