Try the latest dolphin Dev releases. They are often quite stable, as the development process for dolphin means that most issues are fixed before things are merged into master, and there are a number of fixes that may help that we're merged after 5.0
For issues like this, it may be worth seeing if disabling the dual core mode helps. While it can speed some things up, it had fundamental issues and can cause all kinds of problems in games. The same with fractional IRs (though you said there was no change after moving away from 2.5x) Generally, its better to run without dual core if your CPU can handle it, which an i5 7400 should be able to do easily for the majority of games.
For issues like this, it may be worth seeing if disabling the dual core mode helps. While it can speed some things up, it had fundamental issues and can cause all kinds of problems in games. The same with fractional IRs (though you said there was no change after moving away from 2.5x) Generally, its better to run without dual core if your CPU can handle it, which an i5 7400 should be able to do easily for the majority of games.