I've tried combinations of closing and restarting COUTL.EXE but no difference. The only thing that seems to "clear" it is exiting and reloading the sim.
The error in your log, shows a problem while making a Simconnect call to read the variables if the airplane might be frozen, which is done while restarting, to unfreeze it, in case you restarted Couatl while in the middle of a raised pushback, so the airplane won't be left stuck frozen.
If you are sure that, restarting Couatl won't fix it, that it's confirmed (considering you say it mostly happens at landing) it's a problem of Simconnect being unresponsive due to having reached the maximum number of Simobjects in the sim, usually caused by too high AI settings.
As a general rule, if something can't be fixed by restarting the Couatl engine, but restarting the sim fixes it, it's nothing caused by GSX, and it's Simconnect being unresponsive or giving erratic results because of the max Simobject limit.
Here's a post which explain what you can do in GSX to reduce its own contribution to the number of Simobjects in the sim:
https://www.fsdreamteam.com/forum/index.php/topic,30930.msg198089.html#msg198089
