Oral-B IO9 battery issues

My oralb series 9 has been shutting down while brushing with 40-50% charge left. It seems to happen more and more often now and the toothbrush is only 1 year old. I took really good care of it, charging only to 90-93% and discharging not lower than 20%. For such an expensive brush the li-ion battery life is quite bad, considering my older dump electric toothbrush lasted 4 years with minimal battery wear.

Anyone else having this issue?

I read a bit on the forums and it seems that I'm not the only one with this problem:https://www.ifixit.com/Guide/Oral-B+iO+Battery+Replacement/136696