iOS failing to render vcf file

I use twilio to share contact information of my users. I've been doing this for 6 months with no problems.

Recently, I started receiving bug reports that the contact card isn't coming through. iOS is receiving it as an unknown attachment with a file name such as 'text_0.x-vcard' [see screenshot]

I'm unable to reproduce this on my device - I've received reports of this from users with an iPhone 7, iPhone 6, and iPhone 5 - nothing consistent. No consistency in OS either. The vcf file is valid, and it works for 90% of users.

Any ideas? Here is an example of a vcf file - works on my phone, doesn't work on one of the other devices.

BEGIN:VCARD
VERSION:3.0
N:Doe;John;;;
FN:John Doe
ORG:Example.com Inc.;
TITLE:Imaginary test person
EMAIL;type=INTERNET;type=WORK;type=pref:johnDoe@example.org
TEL;type=WORK;type=pref:+1 617 555 1212
TEL;type=WORK:+1 (617) 555-1234
TEL;type=CELL:+1 781 555 1212
TEL;type=HOME:+1 202 555 1212
item1.ADR;type=WORK:;;2 Enterprise Avenue;Worktown;NY;01111;USA
item1.X-ABADR:us
item2.ADR;type=HOME;type=pref:;;3 Acacia Avenue;Hoemtown;MA;02222;USA
item2.X-ABADR:us
NOTE:John Doe has a long and varied history\, being documented on more police files that anyone else. Reports of his death are alas numerous.
item3.URL;type=pref:http\://www.example/com/doe
item3.X-ABLabel:_$!<HomePage>!$_
item4.URL:http\://www.example.com/Joe/foaf.df
item4.X-ABLabel:FOAF
item5.X-ABRELATEDNAMES;type=pref:Jane Doe
item5.X-ABLabel:_$!<Friend>!$_
CATEGORIES:Work,Test group
X-ABUID:5AD380FD-B2DE-4261-BA99-DE1D1DB52FBE\:ABPerson
END:VCARD

Steph, I'm new to Stack Exchange, so I don't know how else to send this. You show one of your Twilio numbers above.
I am seeing similar issues, and I believe it is all related to your content type. Try a

curl --head <your vcard web address>

The only time I've had it work for me is when the it returned

Content-Type: text/x-vcard; charset=utf-8; name="fileName.vcf"

I don't know how long this link will last but try sending this vcard VCF File (Send from http address), it works for me on Twilio w/ iOS 10.3.3

I think your right about it being related to security; why would you want a 'text/html' file being being executed like a 'text/x-vcard' file. I don't think internal header modifiers will work, let me know.