That's interesting. Just for reference, how were you studying tactics? I know chess.com is timed, and some other sites aren't. Some people use books and may go fast or slow themselves. Or like de la mesa do a few over and over for a long time.
I had a stretch where I was spending 15 minutes on each puzzle just for fun... I don't think it helped my tactics because I could only do a few puzzles a day like this, I'm just pointing out some people's habits may be unexpected... so what were your habits?
I posted about this before, but it happened to me again recently. I'm only 1250-1350 rated on 5-min blitz here (that's all I have time to play here), but have fluctuated from as low as 1150 to 1470 in the past several months.
My best play (1400+ range) was when I was not dedicating time to studying pure tactical problems, but was spending my time going over openings, and games from the openings from two books I have.
After getting to an all-time high of 1471, then losing a few games in that range from tactics, I decided to go back to pure tactics for awhile given my limited time to play/study chess (about 40mins/day now) and did that for a few weeks.
When I returned, wow, I was bank in the dumps. Lost gobs of games in a row, and 1200-rated players were beating all over me. I'd get the occasional nice tactical killing win, but most of my games were lost strategically early on, and my rating showed it. I kept studying tactics, thinking it was just a bad stretch, but wow, things got worse and worse. I literally went from 1470 to <1200 in a matter of less than a month, and this was a lot of games, not like just one or two unlucky stretches.
I got a bit depressed over it, but fortunately I remembered how FEW tactics problems I did was playing at 1400 level. I changed my study strategy and started reviewing and trying to memorize full games from Dan Heisman's "Amateur Game Book" which seems about my level, with good annotations.
Things are fortunately slowly starting to turn around. It's no breakthrough by any means, but for sure, I'm playing a lot better than I was at the lo-1200 range. At the least, I'm not 'stuck' at the lo-1200s anymore, which I was when I was all tactics studying pretty recently.
I will add that in studying my games like I am now, I go through quite a few tactical lines in the annotations, so I do get significant tactics review during the games. But it is balanced with the strategy and setups required to get/recognize the tactics.
I'm not saying tactics study is necessarily bad, but I do think that studying tactics at the cost of everything else (de la maza style) can actually be harmful to your chess. At least, it clearly is for mine.
And for what it's worth, my tactics rating on another site went UP to its highest level (1950) when I was at my recent low of 1230 here, so all that tactical know how did NOT translate to wins. In contrast, I was only 1720 on their tactics when I was rated 1471 here, so I clearly wasn't relying mostly on tactics to win games when I things were working. I definitely have to say that at least for me, pure tactics problems training has been the lowest bang-for buck returns I've spent on studying chess, despite what everyone keeps saying about it. Hard for me to admit that, since I was one of those 'all-tactics' study guys, but it's the truth based upon my win/loss results, even in 5-min blitz games where tactics are even more important.
Just some food for thought for you players who seem to be stuck in the low 1200s but are doing a lot of tactics that doesn't seem to help your rating.