Aloha!

I'd guess an edge issue, and/or a technique issue, and/or a sterile issue. I have the opposite problem as you, OP. When I go from my Straight to a Shavette, I have razor burn issues or nicks and cuts. They are a different shave. I have never mastered the Shavette. My straight is so much more forgiving. The Shavette amplifies any of my errors 10 times. Speaking of amplification (magnification);

Here is a video showing a nick in a razor edge that was causing the user irritation. He didn't see this under magnification until he got to about 400 power. SEE AROUND THE 2:30 time Mark in the video;

We may think our edge is great, smooth, sharp and perfect for shaving, but if you have an issue like this, it can cause some irritation.

Yet with all those bumps, it's more like mass irritation. So check technique, check your razor angle (it is different than a shavette - you can get away with a higher angle of attack with a shavette than a straight) and make sure your razor is clean. I am not a germaphobe, but I do put a touch of 70 percent alcohol on my blade after a shave and before a shave. Same with my shavette and DE. Just keeps bacteria and virus at bay.

-Zip