Broken IP addresses in Plesk when 600+ addresses are added to a single interface

Applicable to:

After adding IP addresses, some of them are missing in the interface file.
Missing addresses, as well as some existing ones, are shown in Tools & Settings > IP Addresses as broken.
Repair button does not resolve the error.
Around 600 addresses are added to one interface.

Product issue:

#PPPM-8260 "Users can now manage a large number of IPv6 addresses (more than 600) via Plesk."
Fixed in:
- Plesk Obsidian (RC1 18.0.15 as #PPP-35962) 04 June 2019 (Linux)
- Plesk Onyx 17.5.3 Update 56 10 September 2018 (Linux)
- Plesk Onyx 17.8 Release 17 April 2018 (Linux)

Please consider updating your server:

If update is not possible for some reason you may try the following

temporary solution

Until the bug is fixed, the following workaround can be used for Plesk Onyx 17.5 on RHEL 7/CentOS 7/CloudLinux 7:

Connect to the server via SSH.
Download and unpack attached fix:

# wget https://plesk.zendesk.com/hc/article_attachments/360003173854/ifmng.zip && unzip ifmng.zip
Backup the original file and replace it with the patched one:

# mv /usr/local/psa/admin/sbin/ifmng /usr/local/psa/admin/sbin/ifmng.orig && cp ifmng /usr/local/psa/admin/sbin/ifmng && chmod 750 /usr/local/psa/admin/sbin/ifmng
Repair broken IP addresses via Plesk interface.