How to debug websocket connection error with "Unknown reason"
Looks like someone just filed this as a Chromium (v77) bug. See issue tracking it here.
Update 1: As noted in the issue tracker and comments below, this should now be fixed in the latest stable release, which is being rolled out now (2019/10/11).
Update 2: Despite the bug being marked as fixed/closed in monorail, canary (80.0.3977.4) still appears to have this behavior. As others have noted there is a global limit of 255. However, the fact that connections opened by JS don't get closed/reset when the page is refreshed still seems like a bug to me.
For some very very very odd reason in my computer the websocket connection was considered as an ad by AdBlock.
Try to disable AdBlock and see if it works.