I found another bug: when you click somewhere in the 3d viewport with nothing selected when you are either on the asset placer tab or on something else like output, it gives this error:
/run/build/godot-tools/modules/mono/glue/GodotSharp/GodotSharp/Core/NativeInterop/ExceptionUtils.cs:113 - System.NullReferenceException: Object reference not set to an instance of an object.
at AssetPlacer.SurfacePlacementController.OnSelectionChanged() in [PROJECTPATH]addons/assetplacer/placementController/SurfacePlacementController.cs:line 63
at AssetPlacer.AssetPlacerPlugin.OnSelectionChanged() in [PROJECTPATH]/addons/assetplacer/AssetPlacerPlugin.cs:line 464
at Godot.Callable.<From>g__Trampoline|1_0(Object delegateObj, NativeVariantPtrArgs args, godot_variant& ret) in /run/build/godot-tools/modules/mono/glue/GodotSharp/GodotSharp/Core/Callable.generics.cs:line 39
at Godot.DelegateUtils.InvokeWithVariantArgs(IntPtr delegateGCHandle, Void* trampoline, godot_variant** args, Int32 argc, godot_variant* outRet) in /run/build/godot-tools/modules/mono/glue/GodotSharp/GodotSharp/Core/DelegateUtils.cs:line 86
Once again, none of these bugs actually change the plugin functionality which is great. They just appear in the console which is tedious to always see.