Toggl track downloads the page on refresh

So, I log in and start my toggle track on the web interface. After a few minutes or hours, when I stop a running entry then try to start a new entry or try to restart an existing entry, I see that the timer on the top right does not start to count. I figured that there must be some sync issue, so I try to refresh the browser. This sometimes works.

When it doesn’t work, the following happens: after hitting refresh the browser downloads a file that has a single line in it that says “dhttp2_ handshake_failed”. In this case I usually clear the browser cache and cookies and refresh. That used to work quite reliably, but the past week it stopped working completely.

Occasionally, when this doesn’t work, I just navigate to the top-level domain toggl.com and click the “Go to timer” and that would solve it. But last week the only thing that worked was changing to incognito mode or even to a different browser. But the same story repeated there once I wanted to switch to another entry.

I’m using the web app of toggl track on the Chrome browser on a MacBook. I am on a staged device using a VPN to connect to the corporate network. My initial suspicion was that it is related to the VPN and it frequently reconnecting (e.g. when I go afk and mac goes into screensaver/dark), but since last week it also started happening without going afk.
Any ideas how I could improve the situation?