This problem has always existed before, just not very obvious.
But as the development progressed and the engineering became more complex, the problem intensified.
In order to locate the cause of the problem, I created a simple test scene in the project, but the shadow still keeps flickering.
I tried switching the Display of the Game View twice and it stopped flickering. Switch it again and it flashes again.
Repeated the run many times, the situation is exactly the same each time. It feels like this should be a Unity bug.
After I repeatedly switched Display dozens of times, the character suddenly lost control and moved forward without pressing any keys.
So I created a new project and imported the test scene, but this problem did not occur.
？
I guess it may be a bug in the 2020 version, maybe it will be OK to upgrade to 2021?
In the new version of Unity Hub, when installing Unity it gives me two options, one is the Intel version and one is the m1 version.
I suddenly realized that this is most likely a problem caused by incompatibility of the chip. After I installed the m1 version, the problem was solved.
In addition, although Unity supports m1, the new version of UnityHub does not support m1, so it is very difficult to use.