Need information to help decide when to switch to V9

I would not believe so, no. Unless you think their grievance is due to module issues that have been fixed in v9.

If you could tell us a little bit more about their issues we would gladly help, as we want to provide the best experience to everyone.

When it comes to it, it doesn’t sound like the user is having issues loading the game, but is having issues randomly while playing. Closer to rubber-banding → Taking a long time to load upon clicking (character sheets or journals), or when moving it isn’t very responsive.

I would recommend disabling all modules for troubleshooting. Start your world in safe mode, and see if they still encounter the same amount of issues while playing around. If they don’t, you can try Trouble with Modules

Secondly, make sure they have Hardware acceleration enabled. You can follow this tutorial: How to fix/turn on your browser's hardware acceleration
There is also a related issue with with Intel Graphics and Foundry at this moment.
Have a look at this post and see if it seems related:

Good news for people experiencing issues with webgl and the “always disappearing scene requiring a refresh every few minutes” problem with this graphics setup. Webgl causes the Intel HD 620/630 series GPU to crash following a recent series of driver updates. Rolling back to driver version 27.20.100.8280 will fix the problem. The version under that, 27.20.100.8190, also tested stable, in case that one doesn’t work.

Here are the steps to verify and correct the problem:
Go to WebGL Report in Chrome to check your machine’s webgl capability.
If the unmasked renderer is Intel HD Graphics 620/630 series, go here to run this test to see if the bug exists in the driver you are currently using. Ordinarily this test should run continuously forever. If you have this buggy driver the webgl test should crash after about a minute. This is proof the GPU is crashing. Hello, SciChart.js world!

Solution: Go here and download and install the above mentioned driver version to roll it back. https://www.intel.com/content/www/us/en/download/19344/intel-graphics-windows-dch-drivers.html
UPDATE If you are on a Dell or HP laptop, the above Intel drives will be incompatible. For example if your current driver is version 27.20.100.8854, you will not find that driver among those listed on Intel’s site. The correct driver version to download in this case is 27.20.100.6888 from either the Dell or HP driver download centers. (Note this was tested on HP ProBook 430 G4 Notebook PC).
https://www.dell.com/support/home/en-us?app=drivers
https://support.hp.com/us-en/drivers