I'm a little suspicious as it was a Mazda/Honda stealers that did mine. And I had it back within a day, dropped it off at 9 and it was done by 4. From guides I've read that's barely enough time for the car to cool and the glue on the cover to dry... I might have a go myself next Spring as it doesn't seem that hard, just time consuming.I wonder if they did the valves when the engine was cold? IIRC there are two sets of measurements, one cold and one for a hot engine. If they did it hot and used the cold measurements, It may be that when warm the gap is closing when hot.
Will do in a few days when I'm back at work! Lockdown means I'm probably not driving it until thenTry and get a video of your cold start rattle, it would help us determine if it is a chain noise.