I do not use the latest version of Kaspersky AV Free because, as you rightly say, it causes issues. Version 19 is the one installed, (and prevented from updating to v20), and it has happily coexisted alongside MB (v4.0.4 paid for) and Avast Secureline (paid for) for some considerable time. I have previously tried Defender but without success.
Monday morning all was well and by Monday afternoon, with no W10 or any other program updates (that I could spot) having taken place, that state of wellness was overturned. Why suddenly MB's Web Protection should conflict with Secureline is surely the issue that needs resolution so that the previous harmonious state is restored.
I have also contacted Secureline with this issue, which is known to them, but they are convinced that the solution lies with Malwarebytes, hence my posting.
I will try the beta version of MB and report back.
Thanks