19.5.9.0 exception

[Violet rain]

'A' plugin: possibly trying to use System.Reflection.
error while initializing plugins

and related plugin, error CS0246: The type or namespace name 'A' could not be found (are you missing a using directive or an assembly reference?)

in Ver. 19.4.3.0, it is working without any problem.

[RNN]

Look for an update for that plugin in the official post, without knowing what it is i can not say anything else.
The exception is that in the last version of the TH it prevents using certain "functions" to improve security, and the existing plugins using those functions must be modified to be compatible.