Forget your phone app, most of them are crap, just do a simple test and use your brain.
Fully hand- wind the watch (approx 60 twists of the crown). Check the time versus a reliable source after letting it run for approx 10hrs in dial up position and calculate the rate/day. Wear the watch for 8 hrs and calculate the rate. If all’s well the rate should be between 0 and +10 secs/ day and the rate on the wrist and rate dial- up should be within 5-6 secs.
I’m happy to service the watch if required, but its worth checking it as I suggested first. The Miyota movements are generally OK but they benefit from being run in a high state of wind.