We had an interesting thing happen on a recent Joomla! upgrade which we thought worth sharing.
After the upgrade, some modules located in the same position of the template suddenly started being placed horizontally rather than vertically. This was a bit of a surprise, particularly as it made the logo shrink to the size of the adjacent text so it was practically invisible!
The solution does not seem to be widely broadcast on the Internet but what we noted was that the modules that were still being placed vertically had "Bootstrap Size" on the module Advanced tab set to 0, whereas those that now appeared horizontally were set to 1. This behaviour is as expected - the bootstrap size sets the ratio of column sizes in that position. What was not expected was that it didn't do this before!