Sliding tPAC window by 10 msec

I noticed that sliding the window by 10 msec on a recording, the tPAC results changed drastically. Do you have any ideas as to what could be causing these changes?
(Other randomly selected recordings did not show these changes).

WeTransfer - Send Large Files & Share Photos Online - Up to 2GB Free - You can download the recording from here.


Many factors could be involved: noisy data? window length? actual physiological phenomenon?

We used the same notch filter as in any other case, also checked the tPAC in 10 s long time windows, and got relatively big differences between the two.
We didn't see any actual event while we look through the two 10 ms long recordings.
I attached a screenshot of the two time windows we checked the tPAC in.

There seems to be a lot of non stationarity going on in the recording, with successions of prolonged spindles, one starting about at the end of the time window. I tried to download the data to have a closer look but this seems to require a WeTransfer account. Can you make it more openly available, please?

There shouldn't be a problem with WeTransfer, but I also uploaded the recording to google drive. Here's the link: W75-01.smrx - Google Drive