Hi Mark,
I think that’s an unfortunate part of the process. It reminds me of a Tiger quote. In discussing a swing change, he said something along the lines of:
First I understand it, then it looks better on video, then it feels better, then it performs on the range, then it performs on the course, then it performs in a tournament, then it performs in a major.
https://www.golfsmartacademy.com/golf-instruction/2-ways-monitor-progress/
For me, I often tell my students, bad rounds lead to good practice if you’re paying attention. Some of my biggest technical breakthroughs in the last few years have come following really bad play.
I think the best way to minimize the performance gap, and get your game to carry to the course from the range is to focus on transfer practice. Where you focus on putting your new swing feels into a routine or recipe you can use on the course. Switching clubs, shots, targets are all helpful. Running simulations and putting yourself in a testing/performance environment can also help.
Hang in there! and good luck!
Happy Golfing,
Tyler