I added a locator to our housing fixture before the supervised UR5e trial. The original housings went into the tray cleanly. A replacement housing caught at the tray pocket, though it sat against the same locator. I want to post the improvement without pretending that last part did not happen.
Provided you still have one of the good housings, a side-by-side look costs very little. I would start at the bit that caught, not buy another locator because the first one has embarrassed you.
The new bag says C and the old bag says B. There is a slightly wider lip on C. Our locator contacts a flat further down, so both sit nicely while the lip is in a different place.
Ada, keep the locator result in your post. You changed something useful for B. Erasing that because C turned up would be just as confusing as calling both versions sorted.
The tray drawing only lists B. I have changed my update to say which housings we tried. Thanks, Sam. I was about to turn the whole post into a warning about the locator.