How to fix Uni Gitanjali keyboard layout for bangla?

I use MX21.3 + KDE plasma(v5.20.5). For my native language bangla, I prefer uni gitanjali layout. After I enable it from the “system settings”, I run into a problem. It doesn’t have a আ key. Instead, it showed two এ key. Pressing the qwerty _s_ key should generate __আ__ not __এ__. Is it a known problem? Without switching to another layout how can I fix it?