Multisite Issue with URL

Hello I am working on a client website that is a multisite network, with a primary site then all other multisites are subdirectories.

For all the sites that are run as a subdirectory, at random several times a day, they are having the URL stripped, so for example:

https://www.mysite.com/subsite1, https://www.mysite.com/subsite2, https://www.mysite.com/subsite3 etc.

will at random be overwritten to just

https://www.mysite.com/

Is this a known issue?

Thank you.