Try different apps. Often I find logging to Wahoo Fitness or Cyclemeter, then uploading to Strava, works out better than recording directly to Strava. Fewer glitches too. I rarely rely on Strava to record rides after losing too many rides. Typically if Wahoo Fitness, Cyclemeter and my bike computer say I averaged 16 mph over a 30 mile route, Strava will show it as 14.7 mph. If Strava wants to seduce more middle aged paying subscribers they'd better cater harder to our delicate egos.
And GPS is only approximate so short segments aren't worth worrying about. I've hidden most vanity segments on Strava, those things someone created only 0.1 or 0.2 milettes in shortness and should have set to private. It just clutters up Strava.
The only segments I pay much attention to are around 5-10 miles long, or climbing segments of half a mile to a couple of miles long. There might still be a timing discrepancy of a second or two but it doesn't matter much over the course of a segment that takes 10 minutes to half an hour to finish.
If you want accurate measurements for short segments you could use a speedometer and fumble with the stopwatch feature while sprinting. Or get friends to time starts and stops, then trade off while each takes a crack at the same short sprint zone.
I think I have one "KOM" on a mile long loop, but it's flat so not really a KOM. I quit riding that loop after a fastest time of 20.something mph on a posted 20 mph speed limit residential zone.
Any KOM I can snag isn't worth the effort. I know a dozen guys my age and a few women who could beat my best time pretty much any day. I'm lucky to be solidly middle of the pack on any real climbing segment where a KOM means anything. I'm in the top ten on a couple of climbs but that's mostly due to the relative absence of Strava logs from young pro and amateur riders. The top ten are all either fairly strong but middle aged or older dudes, or two or three women pros. Seems like the young guys on the local pro team don't post on Strava, or don't post publicly so their records aren't displacing us MAMILs. I know they ride these routes because I see them on early morning training rides. But they don't show up on Strava. I reckon they're taking pity on the rest of us.