I submit that there is a bug somewhere. I have seen multiple posts on this where the solution in the end is to "ignore TLS certificate errors". And yes this works for me as well, but this is not ideal when using my device off of the corporate network. A bug was submitted through github, but they were directed to post here.
While some users might be having issues due to Mitm or self signed certs out of ignorance. I am definitely MiTM my connection due to enterprise requirements and I am familiar with this process.
To recreate:
I open my webdav url in a browser and export both crt, cer certificates in the chain to a location on my computer, Then convert them to public pem files, because that is what it appears to handle. (yes i know that they are technically the same file contents, but I used openssl just to be certain)
In the settings I then pointed "Custom TLS certificates" to the location on my computer c:\certs that houses both certificates. I have also tried using a comma separated list to the pem files, but to no avail.
It appears that it is just not applying the "Custom TLS certificates" setting.