there is an issue in the openssl libraries fails if the file size of the crl file is greater then 100kB.
If installation of a newer version is not possible then the crl check can be disabled.
For example the host myDebianRepository.myDomain.org contains the debian repository and has a certificate where the corresponding CRL is greater then 100k.
2 Options to disable the crl check:
Create a file /etc/apt/apt.conf.d/99_myDebianRepository.conf with content
or set the myDebianRepository as trusted
deb [trusted=yes] https://myDebianRepository.myDomain.org/ubuntu bionic main multiverse restricted universe deb [trusted=yes] https://myDebianRepository.myDomain.org/ubuntu bionic-updates main multiverse restricted universe