Exchange 2016 Japanese character not readable

Dear Fellow

I have recently encounter a problem much similar to following.

https://docs.microsoft.com/en-us/answers/questions/394418/exchange-messages-encoding-error.html

My situation however,

1) Some not readable Japanese characters email appears correctly after applying disclaimer using exchange transport rule (new email).

2) 1 of the non problem problematic sender starts having problem after applying the disclaimer (disclaimer was in html format).

I have applied <add key="DisableDetectEncodingFromMetaTag" value="True"> as suggested from following links, however its not helping for situation 2) as above.

https://docs.microsoft.com/en-us/answers/questions/394418/exchange-messages-encoding-error.html

Non readable character looks like following

!&!& (Bｧ $B!& (B

Any suggestion is greatly appreciated. Thanks!