Hi Jaroslav,
I've spent close to four hours trying to help them isolate this issue.
At the request of their Dev/Tech team, I've supplied HAR files, screenshots, DevTools captures and even video recordings of the affected games.
The HAR captures are particularly interesting because they show the problem very clearly. This isn't simply a case of a game "feeling slow". There are enormous delays and bottlenecks within the game-resource delivery/loading sequence itself.
As one example, I've captured the same Pragmatic Play game, CULT, in completely different states:
~78 seconds to load while affected
~14 seconds when working normally
~155 seconds when the problem returned
and later more than 4 minutes in another affected capture
The HAR waterfalls show the difference clearly, including huge gaps between resource-loading stages that simply aren't present when the game is working normally.
I've also now seen similar problems affecting Pragmatic Play, Play'n GO and Nolimit City, while games from other providers continue loading normally. That makes some common part of the delivery/CDN/proxy/aggregation path used by the affected providers an obvious area to investigate.
Every controlled test I've performed has been from a clean browser state, cache and cookies cleared and DNS flushed, and I've also tested different browsers, different internet connections, VPN routing and a completely separate physical device.
So, after supplying all of that diagnostic information, what do you suppose came back from Tech?
"Tell the player to clear his cookies/cache, try incognito, another device and another connection."
Seriously. SMH.
The particularly frustrating part is that my original email to VIP had already documented that I'd done exactly those tests before escalating the issue.
VIP can obviously only do so much with something like this. They're the middleman and generally aren't network/infrastructure engineers. According to VIP, everything I supplied: HARs, tests, screenshots, video and the original technical report, was forwarded intact to the appropriate technical team.
At this point the affected games have repeatedly switched between working normally and being severely degraded while I've been testing them. The HAR captures preserve those different states.
Something in the game-delivery path is clearly behaving very differently between the good and bad states.
But apparently I should clear my cookies again. :)