iTunes Match Artists not grouped right alphabetically

iTunes Match on my iPhone 6 has recently started grouping artists/albums wrong in the alphabetical list in the iOS music app. For example, some artists that begin with "A" are correctly grouped in the 'A' section, however some are pushed into the 'B' section. This continues on throughout my library. On my PC iTunes, everything looks fine and all ID3 tags are as they should be, it just seems to be on the iOS music app. I have gone through several troubleshooting methods including two hours on online chat with Apple Support. So far I have done the following to no avail:

- Switched off iTunes Match on all devices and switched back on.

- Switched off iTunes Match on iPhone only, signed out of iTunes account completely and switched all back on.

- Performed a backup/reset/restore on iPhone incase of a software problem.

- Performed a backup/reset and setup iPhone as "new" incase of issue with backup or other information on device.

- Deauthorised all devices associated with Apple ID and authorised only PC and iPhone.

- Removed albums from library and Match from when I first noticed issue occurring.

- Removed entire library from iCloud and synced with fresh, blank library, then reuploaded to Match (this took nearly four days in total).

I am stuck and at the end of my tether, hoping someone has seen this before and can suggest a fix. I have seen a similar issue reported a few times where it has been one artist or album causing the problem. This is different as it seems to affect the entire library and not just one entry. See the screenshots below for this: