Files attached in Request Revisions not appearing as attachments in emails

Describe the issue or problem
We’re experiencing an issue with our OJS 3.4.0-7 instance where files attached to the email during the Request Revisions process are not actually being attached to the email when sent. In some cases that the user reported this is because the attachments are too big and are getting stripped out by Postfix but in others, the files are well below the size limit and simply aren’t getting attached.

Steps I took leading up to the issue
Go to a submission at Review stage

  1. Record Decision → Request Revisions.
  2. Go to Attach Files.
  3. Go to Attach Review Files.
  4. Check one or both files from reviewers to be attached and Attach Selected.
  5. Continue through to send the email.

What application are you using?
OJS 3.4.0-7

Additional information
No errors related to mail in the PHP log.

An example postfix log is below:

Mar 23 13:35:25 HOSTNAME postfix/smtpd[2136759]: connect from localhost[127.0.0.1]
Mar 23 13:35:25 HOSTNAME postfix/smtpd[2136759]: E91D520534DE: client=localhost[127.0.0.1]
Mar 23 13:35:25 HOSTNAME postfix/pickup[2136509]: EC561589: uid=1131635 from=noreply@ed.ac.uk
Mar 23 13:35:25 HOSTNAME postfix/smtpd[2136759]: EE35C2053478: client=localhost[127.0.0.1]
Mar 23 13:35:25 HOSTNAME postfix/cleanup[2136761]: EC561589: info: header Subject: Editor Decision from local; from=noreply@ed.ac.uk to=twh5@humboldt.edu
Mar 23 13:35:25 HOSTNAME postfix/cleanup[2136761]: EC561589: message-id=2beea5a40d84ae3d7aa33d2b2a58c3a0@ed.ac.uk
Mar 23 13:35:25 HOSTNAME postfix/qmgr[2136510]: EC561589: from=noreply@ed.ac.uk, size=104266, nrcpt=1 (queue active)
Mar 23 13:35:25 HOSTNAME postfix/pickup[2136509]: EF6A077A1F: uid=1131635 from=noreply@ed.ac.uk
Mar 23 13:35:25 HOSTNAME postfix/cleanup[2136761]: EF6A077A1F: info: header Subject: Editor Decision from local; from=noreply@ed.ac.uk to=
Mar 23 13:35:25 HOSTNAME postfix/cleanup[2136761]: EF6A077A1F: message-id=541ea9d2af7d8ad7d4d79d5eedd777e1@ed.ac.uk
Mar 23 13:35:25 HOSTNAME postfix/smtpd[2136759]: F0B6B20534DE: client=localhost[127.0.0.1]
Mar 23 13:35:25 HOSTNAME postfix/qmgr[2136510]: EF6A077A1F: from=noreply@ed.ac.uk, size=1594, nrcpt=1 (queue active)
Mar 23 13:35:25 HOSTNAME postfix/pickup[2136509]: F146377A8E: uid=1131635 from=noreply@ed.ac.uk
Mar 23 13:35:25 HOSTNAME postfix/cleanup[2136761]: F146377A8E: info: header Subject: Editor Decision from local; from=noreply@ed.ac.uk to=
Mar 23 13:35:25 HOSTNAME postfix/cleanup[2136761]: F146377A8E: message-id=6ba5399648ef90c986fa849543a4c4b4@ed.ac.uk
Mar 23 13:35:25 HOSTNAME postfix/qmgr[2136510]: F146377A8E: from=noreply@ed.ac.uk, size=1596, nrcpt=1 (queue active)
Mar 23 13:35:26 HOSTNAME postfix/smtpd[2136759]: disconnect from localhost[127.0.0.1] helo=1 mail=3 rcpt=3 data=3 quit=1 commands=11
Mar 23 13:35:31 HOSTNAME postfix/smtp[2136765]: EC561589: to=, relay=MAIL RELAY ADDRESS[MAIL RELAY IP]:25, delay=5.7, delays=0.03/5/0.01/0.66, dsn=2.0.0, status=sent (250 2.0.0 62NDZVg4954711 Message accepted for delivery)
Mar 23 13:35:31 HOSTNAME postfix/qmgr[2136510]: EC561589: removed
Mar 23 13:35:37 HOSTNAME postfix/smtp[2136765]: EF6A077A1F: to=, relay=MAIL RELAY ADDRESS[MAIL RELAY IP]:25, delay=11, delays=0.01/11/0.01/0.36, dsn=2.0.0, status=sent (250 2.0.0 62NDZarn954986 Message accepted for delivery)
Mar 23 13:35:37 HOSTNAME postfix/qmgr[2136510]: EF6A077A1F: removed
Mar 23 13:35:42 HOSTNAME postfix/smtp[2136765]: F146377A8E: to=, relay=MAIL RELAY ADDRESS[MAIL RELAY IP]:25, delay=16, delays=0.01/16/0.08/0.31, dsn=2.0.0, status=sent (250 2.0.0 62NDZgNV3906509 Message accepted for delivery)
Mar 23 13:35:42 HOSTNAME postfix/qmgr[2136510]: F146377A8E: removed

I’ve done more testing on this and discovered that the user added as Author in the Participants panel receives the attachments but the Contributors (even the Primary Contact) only receive the email text and no attachments. Is this the intended OJS behaviour?