First of all, thanks for writing sane software, and yes I do realize that this can be a problem with OpenVPN and/or TAP drivers, but bear with me.

Quite a while ago I had tixati version 2.55 working good with autolimit enabled (pinging VPN server actually), on this same OS (updated 64bit Windows 7) and this same VPN.
Due to unrelated reasons earlier I switched autolimit off - wasn't needed for a while.
Now I want to not only limit outgoing traffic (which works absolutely fine, mind you) but also limit/prioritize incoming traffic. This doesn't work as intended.

As soon as I enable either "Limit Incoming KB/s" (with arbitrary sufficiently large number at least 4x of intended throttle) or "Auto Limit" (with same old proven-working config) - not only my traffic drops to about 35 kb/s, but pings to VPN endpoint grow from ~30ms to ~260ms and seldom fall below ~150ms while any incoming limiter is enabled. As soon as I disable incoming limiter(s) - ICMP ping RTT returns back to normal, and incoming traffic starts to pass with "normal" speed.

Yes, enabling incoming limit in tixati makes entire VPN link slow as hell. Outgoing limiter works apparently fine. BitComet limiting works fine too. I use core affinities and I do prioritize OpenVPN above norm.

I tried downgrading tixati, but unfortunately I have no tixati-2.55-1.win64-install.exe laying around anymore; version 2.56 displays the same (erroneous) behavior.

Advanced socket options say this: // Name:  Compatible (DEFAULT) \n // Updated Aug 9, 2014 - haven't changed anything there.

What can be done from my side to pinpoint the problem? I'm willing to debug.

* * *

Now I must confess that between 2.55 and 2.65 timeframe I updated OpenVPN to latest stable version. I believe that TAP-Windows driver was updated too during that process. I will of course try to downgrade OpenVPN and its companion TAP driver - only this process is much more time-consuming than downgrading tixati and testing with lower version of it (which I already did from 2.72 all the way back to 2.56 - earliest that Your server still has, it seems).

Still I strongly believe that enabling incoming traffic limiting in ANY application program should NOT make entire network link slow, neither should it interfere with said link's packet RTT.

Nobody?

Seems like I'm not the only one with this problem, for example see Mixer's post in "Usefulness of the Auto-Limiter" thread.

Lucky you, the 2.55 version is still available on the internet archive https://web.archive.org/web/20171116071250/https://download2.tixati.com/download/tixati-2.55-1.portable.zip
I use the same config yet not updated OpenVPN in a while (nor do i have all the latest and part-broken windows updates) and everything works. I ping the VPN server directly via the tunnel, not through the public internet. Here's my openVPN driver version:
Relevant config directives (client):

client
dev tun
proto udp

What happens if you ping ipv4/v6 yourself in console?