Speakers - both channels out of one speaker

hi everybody,

I have very weird problem and wonder if someone else had similar experience. I have Macbook 12inch 2017, before the problem itself small note: I have my to-case replaced recently. I don't know if this is anything to do with the speakers tho anyway. Recently I discovered that my left speaker does not work, I have checked the midi utility, it is how it supposed to be. Controlled the pan, its balanced. The weird part is I slide the pan bar to left so verify my left speaker is down, the sound still comes out of right speaker but the sound is muffled. When the pan is on right, right speaker works normally. To sum up, left speaker is down, left channel comes from right but muffled, right works alright.

Tried resetting SMC NPRAM etc... no luck, I have been thinking to reinstall the OS but its a workload and wanted to ask you guys first. Do you think its a software problem? should go to apple store which is quite far from where I live.