I gave this a try on my end in a few browsers including Brave (freshly installed) with the old and new theme. The main difference is I chose 30MB instead of 200MB for the download as my connection is a lot slower.
In Brave, Chrome and Firefox with the old theme, it ran tests #1, #2 and #3 and skipped tests #4 & #5. However, it did not restart or get stuck with any test.
I tried with the new theme in Chrome with the same set up and it ran all 5 test iterations.
To double-check it was skipping tests #4 and #5, I took a screenshot on the third iteration in the old theme:
After it ran this third combined test at the 9:04pm, it showed 'Done!' followed by an e-mail. The following is the results page showing the three combined tests and an arrow pointing to the third test time. Interestingly the tab shows 'Test 5 of 5' even though it skipped #4 and #5: