How do you know ? Do you continuously monitor the line itself, or is it just that nothing else crashed at the time ?
(TL/DR at end)
I had a similar problem at intervals for a long time (years in fact), especially in bad weather. The engineers could never find anything as they only ever arrived on nice days… I created a monitor (a script on my Linux system) which 'ping’ed the IP-address of the ISP’s end of my connection every 15 seconds continuously - it was quite enlightening. Sometimes there would be long periods of no drop-outs at all, but in bad weather the drop-out rate and duration would increase markedly. There were primarily 3 drop-out durations - 15 seconds, 2 minutes and 10 minutes, talking to the engineers I discovered that this was characteristic of my type of connection (fibre to a local cabinet, copper from there to my house), the different times being down to how severe the drop-out was. An engineer finally visited on a bad-weather day, immediately detected a fault in the overhead copper wire about 100 yards from my house, and subsequently found a bad connector with water ingress and corrosion problems at the relevant place on the wire. Since he replaced the connector I’ve had almost no drop-outs at all.
The point of this tale ? I found that :
The 15-second drop-out almost never caused any problems, a slight hesitation in Eve, perhaps a buffer-delay in Youtube or Netflix, or a slow page-load in the Browser.
The 10-minute drop-out always caused Eve to fail, Netflix etc to need re-requesting, and reasonably static browser pages usually gave a ‘missing server’ message so I had to retry.
The 2-minute drop-out was the erratic one, sometimes leaving Eve frozen, the client remaining active but the connection to the server obviously lost. This was inconsistent across multiple clients when multi-boxing - I run up to 3; sometimes they’d all drop, sometimes none, sometimes only 1 or 2 would stall while the others carried on perfectly. Youtube, Netflix and Browser reactions were similarly inconsistent.
TL/DR - Don’t assume that your connection to your ISP is OK just because you don’t see problems with other activities, or because your connection provider and ISP can’t find a fault. I had this problem for several years, getting worse each winter, and finally had to monitor the line myself and insist on a bad-weather engineer visit before what turned-out to be a simple physical problem was finally fixed.