Warp Stabilizer laggy AFTER footage stabilized

A friend of mine sent me this video and said when he applies Warp stabilizer of the footage Premiere plays it back with huge lags. So that means after the footage was stabilized. If he renders in and out points the lags disappear, the exported footage also has no lags. Here’s how it looks:

In the video the stabilized is the upper shorter clip.

I would have not posted this but for one thing - his PC does not even sweat when playing back the stabilized footage but it makes it lag. In the video below you will see the performance tab pf the windows process manager, see the loads of the components. I would not say the footage is any problematic for this PC at all. So what can be the cause of this bug?

Pr 26.2.2, Win 11 25h2, 32 Gb Ram, RTX 5060Ti, SSDs, i9-9900k

Footage:  MP4/MOV H.264 10 bit 4:2:2 - it’s a NV 50xx GPU-decoded format so the card should be enough to play it back flawlessly.