Hi, The problem happens with Unity 2021.3.5f1 LTS and 2021.3.6f1 LTS, and TextMeshPro 3.0.6. I have several elements in my UI with TMP Text Components. Everything was working fine for many weeks (I believe it was before I upgraded to Unity 2021.3.5f1 LTS). Yesterday, I noticed that the custom font I had set in the components, was being swapped, during Play mode, with the default TMP font "out of the blue", and for no apparent reason. In Edit mode, there's no problem, the fonts are set correctly. Moreover, the "swap" doesn't happen all the time. Sometimes, there's no swapping, but quite frequently, the fonts are swapped, and when they are swapped, they are not swapped for all the components using that font. I re-imported and re-created the custom fonts, and made sure that the fonts are in a Resources folder. The only change that I can probably relate to (besides upgrading from Unity 2021.3.4f1 LTS to Unity 2021.3.5f1 LTS), is that I was using the Canvas as a prefab, and I unpacked it a couple of days ago. I did just an "unpack, not "unpack completely", but the UI elements with TMP Text, which are children of the Canvas, were not a prefab themselves anyway.