TV reception conditions are affected by, among other things, the 11-year solar sunspot cycle. That's currently heading up towards a peak, so the conditions now won't be the same as they were a few years ago. That could well explain why you're now getting signal strength problems that you've not had before.
Further, Freeview television is transmitted using 'multiplexes', which are 'bundles of channels', with each multiplex using a different frequency. Channel 101 is transmitted using the PSB3 multiplex, whereas Channel 832 is included within the PSB2 one. It's likely that your aerial is closer to 'resonance' on the PSB2 frequency than on the PSB3 one, explaining why you can receive the data signals OK on Channel 832 but not on Channel 101.