It's been several years since I worked with Manjaro, so I don't remember which specific apps I ran into problems with, but the general idea is this:

Manjaro holds back packages for several weeks behind vanilla Arch, so packages from the AUR are often built on versions of their dependencies that aren't yet available to Manjaro users. This can result in apps not installing properly (or at all), or apps that were previously installed without issue suddenly breaking when they attempt to update.

This isn't actually specific to Manjaro -- other Arch-derivatives like Garuda can also run into this problem. You'll find that any Arch-based distro that makes significant changes to Arch (like holding back packages, or distributing versions of packages different to the ones in the Arch repositories) can have issues if it's attempting to use things from the AUR. Arch derivatives that make no changes to the base system, and just use the vanilla Arch repositories don't have this problem. Endeavour OS is an example of this, as the only changes it makes are additive -- they have their own extra packages, but don't change any core functionality from vanilla Arch.

EposVox on youtube ran into some issues with Garuda about a year ago, and those are of the same flavor as what I experienced on Manjaro, even if they aren't identical issues.