Unlike your previous question on disabling plaintext login on POP3, to fix this vulnerability you have to install patches from Microsoft and it always involve the risks of breaking things. (Especially when KB4295699 is update rollup that includes multiple updates)
The only advice I can give you is to setup test installation (by cloning the production server) to an isolated environment, then install the update and test various functions, and see if anything breaks.
However quick search on KB4295699/KB4099855/KB4099852 didn't return any cry-out for fails, so if the patch can be installed it should be safe.
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Btw, the next time you see issues returned by Nessus, why don't you try do your homework to decide whether you should install the fix or not? IMO this is what your employer pays your salary for. Setup test environment, plan ahead for test-case to be included, validate updates, and plan how to execute the updates are all essential skillsets for MIS staffs.