If you have both, depending on the series popularity (which I cannot explain why), putting the year of the older series in its name, aids greatly with proper match automatically.
Also, it it important to remember, when renaming in-situ, PMS might/can/tends to remain ‘locked on’ to the original name. It is always best to move away from PMS (another location), update library, empty trash, clean buffers, rename in other location, then move back and obtain a fresh match.
Names correctly, manual matching is not needed, as in:
[chuck@lizum /syno.103]$ ls tv*/*Flash*
tv/The Flash:
Season 01/
tv/The Flash (2014):
Season 01/ Season 02/ Season 03/
[chuck@lizum /syno.104]$