Gmail is removing attachment from multi-part mime email for some recipients

I have a strange situation where gmail seems to be removing an email attachment, but only for specific recipients.

1. Create a calendar invite from bob@domain.zzz and emal to sarah@gmail.com and tom@gmail.com
2. Reviewing the source for the received messages for sarah@ and tom@, the messages are identical except the mime attachment below is present for tom@, but missing from sarah@:

--_=_swift_v4_1579834073_2cce74c64a50735eba644772892c3510_=_
Content-Type: text/calendar; method=REQUEST; charset=utf-8; name=event.ics
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=event.ics
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OkZSRVE9WUVBUkxZO0JZREFZPTFTVTtCWU1PTlRIPTExDQpFTkQ6U1RBTkRBUkQNCkJFR0lOOkRB
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MDANClRaT0ZGU0VURlJPTTotMDUwMA0KVFpPRkZTRVRUTzotMDQwMA0KUlJVTEU6RlJFUT1ZRUFS
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SFQNCkJFR0lOOkRBWUxJR0hUDQpUWk5BTUU6RWFzdGVybiBTdW1tZXIgVGltZQ0KRFRTVEFSVDoy
MDA3MDEwMVQwMjAwMDANClRaT0ZGU0VURlJPTTotMDUwMA0KVFpPRkZTRVRUTzotMDQwMA0KUlJV
TEU6RlJFUT1ZRUFSTFk7QllEQVk9MlNVO0JZTU9OVEg9Mw0KRU5EOkRBWUxJR0hUDQpFTkQ6VlRJ
TUVaT05FDQpCRUdJTjpWRVZFTlQNClVJRDozNTcxMmI4YS04OTI5LTQ4Y2YtOTE1YS1hZjc1ODMw
NDUwZGMNClNFUVVFTkNFOjENCkRUU1RBUlQ7VFpJRD1BbWVyaWNhL05ld19Zb3JrOjIwMjAwMTI3
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RDoyMDIwMDEyNFQwMjQ3NTRaDQpEVFNUQU1QOjIwMjAwMTI0VDAyNDc1NFoNCkNSRUFURUQ6MjAy
MDAxMjRUMDI0NzU0Wg0KU1VNTUFSWTpnbWFpbCB0ZXN0IHRvIGNwIGFuZCBwbXANCkFUVEVOREVF
O0NOPVBhdHJpY2sgUHJpdGNoYXJkO1JTVlA9VFJVRTtQQVJUU1RBVD1ORUVEUy1BQ1RJT046bWFp
bHRvOnRlbmRpbQ0KIEBnbWFpbC5jb20NCkFUVEVOREVFO0NOPUNocmlzdGluZSBQcml0Y2hhcmQ7
UlNWUD1UUlVFO1BBUlRTVEFUPU5FRURTLUFDVElPTjptYWlsdG86Y2hyaQ0KIHN0aW5lLmt3dW5A
Z21haWwuY29tDQpPUkdBTklaRVI7Q049UGF0cmljayBQcml0Y2hhcmQ6bWFpbHRvOnBhdHJpY2tA
ZDI2Lm5ldA0KQ0xBU1M6UFVCTElDDQpFTkQ6VkVWRU5UDQpFTkQ6VkNBTEVOREFSDQo=

--_=_swift_v4_1579834073_2cce74c64a50735eba644772892c3510_=_--

Since the email is going to both sarah@ and tom@ and they are both using gmail addresses, I expected the content to be the same.

Any ideas what could be wrong?