Using 5.5.8404 I extracted the dll and placed it in the plugins directory. I then placed the problem custom preset in \AppData\ASR Presets. Note that this has an extension of .ASR Preset.xml. I opened MB, opened ASR and clicked on "import new" and got this error. Note that it's looking for the presets under the Plugins directory, while your most recent reply states they could go under AppData.

I noticed that while the time stamp on the problem preset had not changed, the extension did change to .asr-preset.xml, so I selected 'import' and got this error:

I then moved MusicBee\AppData\ASR Presets to \MusicBee\Plugins\ASR Presets, I placed the problem preset, with its original extension (.ASR Preset.xml) in the "new" presets directory and launched MB, followed by opening ASR which showed no presets. I clicked 'import all' and 117 of the 118 presets were imported. The one that did not import is the problem one. And this time the file extension did not change to the new format.
With the presets in Plugins\ASR Presets each time I launch MB and open ASR the presets are missing and I have to 'import new.' [EDIT: This may be because I failed to 'Save All & Close'] For the time being, I moved them back to under the AppData directory and things are back to the way they were.
I will upload the problem preset to MediaFire and PM the link to you shortly.
Thanks.