Irregular requests to a blocked site #713

When I do action like "go backwards" or "reload current page" than uMatrix doesn't work (irregulary). I can not figure it out for a couple of months, but it happens. I see it in my outgoing network connections log (firewall), that Firefox make requests to a sites blocked in the uMatrix. Usually it is a google-analytics.com, googletagmanager.com etc.
Sadly I cann't define and describe it properly here, like a proper bug report. But it is something to look at for a developers and give attention, because it is a data leak.

How to reproduce it:

1. create a general domain blocking rule e.g. google-analytics.com
2. use application firewall, http proxy etc. with logging enabled
3. browse web sites like usual
4. from time to time (daily just few times in my case), there will be a request to blocked site in the log...

Tech. info:
I use uMatrix 0.9.3.6 with referrer and UA spoof.
And Firefox 45 with Javascript: enabled; Cookies: enabled; Java: disabled; Plugins: none; Extensions: many, but tested as unrelated to the problem; Cache: enabled.