I also noticed that large log files are created (> 200 MB) and found out about logging causing some of the memory problems (see here and here). To turn off most of the logging, I used this in a JS code chunk in Begin Experiment (the code snippet mentioned here did not work for me):
psychoJS.experimentLogger.setLevel(core.Logger.ServerLevel.CRITICAL);
HOWEVER, this still does not resolve the extensive RAM demand. While it seems to slow down the RAM hunger, I am running into the same issue eventually - just at a later time. After experimental Block 13, it is already consuming 13 GB.