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Yes, I am familiar with Fr Trinh and his situation, God rest his soul..

When he separated from the Society, a group was interested in having him as their priest.
 They wanted proof that he was conditionally ordained.
 So, Fr Trinh wrote Bp Fellay-no response.
 He wrote one of the higher ups at Econe-no response.
 Finally, he wrote the US District Superior.
Well, for whatever reason(maybe just because it would only cost the price of 1 US stamp) he got a response from him.
 The Superior sidestepped the question at hand, to provide Fr Trinh with his certificate, and had the gall to tell him that if the group he has contact with needs a priest, that this group should contact the SSPX and perhaps they could help them out.

While he eventually was again conditionally ordained by Bp Slupski, and then Consecrated, some time after that group showed interest, a family member found the photos 📸 of Fr Trinh's conditional ordination.
 The picture shows Fr Trinh  in a folded Chausable  kneeling before Bp Fellay, who is in Pontificals. This only happens when a man is being ordained to the priesthood.

It was too late for Fr Trinh to work with that group, but was furthur vindication of his claim.

May his priestly soul rest in peace.

I doubt this because much more recently Fr. Zigrang has been asked his thoughts about the Resistance and one of his responses is something to the effect of "they think I'm not a priest".