Check your electrical connection/socket in which speakers are used to see if there is any wiring/ground issue. Also, entry tier speakers don't last very long so if your speaker last from 2018 till now then it already is a very good performance.
Wiring/earthing is all good, nothing happens till today to any electrical products like burring, shock or fuse etc., even conventional bulbs/tubes too last for 3-4-6 yrs.
I have once basic test, accidently found, to check earthing, in past got minor tingling shock from my PC Cabinet screws and when I asked electrician, he came and correct earthing, after that I again test and no current from cabinet screws and till today still no such minor/tingling current I experience from those screws so can say no earthing issue at least.
Yes, but in last May-June for 15-20 days, there is lots of electricity flicker issue, whole house bulb/tubes keep flickering all days, UPS to keep make noise like tick-tick, latter we noticed that it's due to some fuse issue in Society Meter Box and one day the fuse blown-up and society change it with branded Anchor Fuse, after that no such flicker issue since start of monsoon.
Is it good to power up Speaker from UPS, I have UPS for PC and one 3 pin socket in 'APC VA 600 UPS' is unused?