If you are experiencing this issue on Catalina and have Kaspersky anti-virus software installed, the only solution is to temporarily disable it ("Turn Protection Off") and contact Kaspersky's support for further assistance. Even though the kernel panics occur when opening an encrypted file in the Boxcryptor drive, they are actually caused by Kaspersky's com.kaspersky.kext.klif kernel extension and not by Boxcryptor.
The kernel panic logs contain the following entry:
Kernel Extensions in backtrace:
BSD process name corresponding to current thread: kav
I'm sorry, but there's nothing we can do here from our side and Kaspersky needs to fix their software.