In 1971 IPC's popular title Sally had a break in publication of several weeks. I don't know the cause of this, and as it is both obscure and pre-internet, it's not something you can just look up on Wikipedia. The assumption is that this was due to a strike, since the 1970's were plagued with them. Every other week someone was striking about something.
I also don't know how long the break lasted, but it was long enough to have a cover celebrating its return, and a message from the titular Sally apologising for her absence.
Says comics buff Phil Rushton:
When it first appeared in June 1969 IPC had great ambitions for Sally which, as far as I'm aware, was the first title to reflect Gerry Finlay-Day's fresh approach to girls' comics (though the original editor was listed as Lennox Wenn). Unfortunately, such a long absence from newsagent's shelves must have had a crippling effect on the circulation of this relatively new comic (no doubt many readers had long since jumped ship to DC Thomson's more reliable Bunty). As a result, the very issue that saw Sally's return also featured an advert for a brand new weekly that was to be released the following week with all the advantages of free gifts and a high-power publicity campaign. This, of course, was Finlay-Day's own Tammy.
Did anything of Sally survive long in Tammy, once they'd merged? I don't know, though I expect to find out shortly. I do know that Sally didn't get to share Tammy's masthead for long. It needed the room for the next comic it claimed....