The filter is a great idea.
The filter is a great idea. There’s no need to pass frequncies over 1 GHz into or out of the home and pollute the spectrum at which MoCA will operate. SJMaye’s units also do not support encryption from what I recall.
I am surprised though with the result. Can you explain how the filter is connected in your coax network? Also, for a channel that you are experiencing an issue with, can you monitor the signal level and signal-to-noise both with and without the filter applied to see if you can notice the difference in that reagrd? What frequncy (or frequency range) is the channel you are seeing troubles with? Are you sure that the filter is the cause? Was the issue happening so frequently that you can tell with certainty that removing the filter immediately solved the issue or could it be intermittent such that you may need to wait some amount of time to determine the effect?