I got sick of the time-of-day clock in the IC-R100 running fast - about a minute a day on mine. The fix is fairly simple, needing two 15pF capacitors to be soldered in parallel to two existing SMD capacitors on the front panel PCB. It slows down the 32768 Hz crystal just enough to bring it almost perfectly on time, now it runs only about a quarter of a second fast per day.
There's a fair bit of disassembly required to gain access to this area of the PCB, so be prepared for that. Also, have a cheap lint-free cloth & cheap small paint brush available to dust off the LCD and inside of the plastic display lens before reassembly... nothing worse than putting everything back together and then spotting a bit of fluff or dust specks on the inside of the display!
If you're so inclined, this would be a good time to replace the incandescent light bulbs illuminating the display with long-life LEDs too.