Hmm,
Assuming you opened the XML published above
<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
<!DOCTYPE fcpxml>
<fcpxml version="1.2">
<project name="TEST PROJ mc">
<resources>
<asset id="r8ADB4FF2-66F9-43F3-8DC7-95B1337E869B" name="AUDIO TEST.WAV" src="file://localhost/Users/Homley_1/Desktop/TEST/AUDIO%20TEST.WAV" start="06;19;26;02"/>
<asset id="rA6CDC090-4634-41F2-93E8-F7CA9387A701" name="9S3A1041.MP4" src="file://localhost/Users/Homley_1/Desktop/TEST/9S3A1041.MP4" start="07;08;30;17"/>
<asset id="rF7E90FF0-AFE9-4BAE-A448-3B19E44EC510" name="9S3A1044.MP4" src="file://localhost/Volumes/21%20BACK-UP%20/2020%20WEDDINGS%20IN%20WORK%20/VILIANE/FOOTAGE/CAM%20A/9S3A1044.MP4" start="07;12;29;06"/> ...
And look at the error meassage from above
Encountered an unexpected value. (src="file://localhost/Users/Homley_1/Desktop/TEST/9S3A1041.MP4": /fcpxml[1]/project[1]/resources[1]/asset[2]/@src)
The media file cannot be imported. An offline clip was not created because of insufficient data. (duration=<empty>: /fcpxml[1]/project[1]/resources[1]/asset[2])
You'll see that: asset instance 2 in (resources instance 1 for project 1) misses duration.
So find (using TextEdit or better BBEdit) this asset.
<asset id="rA6CDC090-4634-41F2-93E8-F7CA9387A701" name="9S3A1041.MP4" src="file://localhost/Users/Homley_1/Desktop/TEST/9S3A1041.MP4" start="07;08;30;17"/>
So for testing you might add a duration="10s"
<asset id="rA6CDC090-4634-41F2-93E8-F7CA9387A701" name="9S3A1041.MP4" src="file://localhost/Users/Homley_1/Desktop/TEST/9S3A1041.MP4" start="07;08;30;17" duration="10s"/>
The next import test will give you:
Encountered an unexpected value. (src="file://localhost/Volumes/21%20BACK-UP%20/2020%20WEDDINGS%20IN%20WORK%20/VILIANE/FOOTAGE/CAM%20A/9S3A1044.MP4": /fcpxml[1]/project[1]/resources[1]/asset[3]/@src)
The media file cannot be imported. An offline clip was not created because of insufficient data. (duration=<empty>: /fcpxml[1]/project[1]/resources[1]/asset[3])
So asset 3 has missing duration. Find and enter the dummy duration and you get this error:
Encountered an unexpected value. (src="file://localhost/Users/Homley_1/Desktop/TEST/AUDIO%20TEST.WAV": /fcpxml[1]/project[1]/resources[1]/asset[1]/@src)
The media file cannot be imported. An offline clip was not created because of insufficient data. (duration=<empty>: /fcpxml[1]/project[1]/resources[1]/asset[1])
Same procedure again results in a kind of import with these errors
TEST PROJ_multicam dur test.fcpxml Invalid edit with no respetive media. (/fcpxml[1]/project[1]/resources[1]/media[1]/multicam[1]/mc-angle[1]/clip[1]/video[1]/audio[1]/audio[1])
TEST PROJ_multicam dur test.fcpxml Invalid edit with no respetive media. (/fcpxml[1]/project[1]/resources[1]/media[1]/multicam[1]/mc-angle[1]/clip[1]/video[1]/audio[1])
TEST PROJ_multicam dur test.fcpxml Invalid edit with no respetive media. (/fcpxml[1]/project[1]/resources[1]/media[1]/multicam[1]/mc-angle[2]/clip[1]/video[1]/audio[1]/audio[1])
TEST PROJ_multicam dur test.fcpxml Invalid edit with no respetive media. (/fcpxml[1]/project[1]/resources[1]/media[1]/multicam[1]/mc-angle[2]/clip[1]/video[1]/audio[1])
TEST PROJ_multicam dur test.fcpxml Invalid edit with no respetive media. (/fcpxml[1]/project[1]/resources[1]/media[1]/multicam[1]/mc-angle[3]/clip[1]/audio[1])
TEST PROJ_multicam dur test.fcpxml Invalid edit with no respetive media. (/fcpxml[1]/project[1]/resources[1]/media[1]/multicam[1]/mc-angle[3]/clip[1])
So since I worked with dummy values these errors are expected.
To get the real world values for assets 1 thru 3 (AUDIO TEST.WAV, 9S3A1041.MP4, 9S3A1044.MP4) create a new lib, name an event and import those assets then export as XML.
Copy the asset start and duration values and replace the dummies from above.
You can post the XML here.
P.S. I don't now whether the start TC in this Plural Eye does work at all.