A question and an observation.
One, are you using instant cast?
Two, you're playing on around 90-100 ping in the first clip. Mo's ult is technically not instant, just very fast. It takes around 10 ticks to come out in a 64 tick game, or ~156ms. Between Combo's startup time and the ping, Shiv...
Resistances stack diminishingly, not additively. You can check out the Deadlock wiki to see the calculations. https://deadlock.wiki/Damage_Resistance
That said I don't think there'd be any harm in the game showing you an additional tooltip of how much resistance you're actually going to get...
After looking inside of abilities.vdata, I suspect the problem is with the conditional on the resist. It appears to be missing a condition hook and so the spirit res is simply being ignored, because the conditional isn't being met.
I'm not really sure why it's conditional in the first place...
Also can confirm, tried it on multiple heroes. Double checked to make sure that it wasn't just the damage numbers that were bugged, but all spirit damage seems to do the same exact damage with or without scourge.
Another thing that can cause this is the following:
Enter the "ESC" menu
Press and hold the TAB key
While holding the TAB key, press ESC
The UI will be stuck.
The current workaround I found is simply tapping the TAB key while in the ESC menu.
Not a high priority problem (you can always just launch the game without a controller plugged in), but I've accidentally launched this game a couple times with an Xbox-type controller. If at any point I had it plugged in after launching the game, even after disconnecting it, clicking will not...
Can confirm, had someone doing this in a match and exploiting it today. It looks like it's using the slide animation/momentum, but since you're in a special state you're not using any stamina and it lasts infinitely long.
Pretty gamebreaking on Infernus as is.