Problem using Screen Time for Roblox (Catalina and Big Sur)

We use screen time to help my son shut off Roblox (he really likes the 5 minute warning and that he can ask for an additional minute). While it works fine on his ipad, on our macbook air its very glitchy. In both Catalina and Big Sur it causes the Roblox window to rapidly flash, and the only way I've found to get out of it is to press the power button to shut down the computer. In Big Sur, when he asks for the extra minute, the cursor stops working (this doesn't seem to be an issue in Catalina). Anyone experienced something similar and found a way to fix it?