i am try to do packing slip posting for sales order, all the setups are done , inventory is available but getting one generic error "Exception has been thrown by the target of an invocation."

NOTE: this error persists for all sales order packing slip posting, other processes are working fine.
Tried to debug the issue and got that this process exits out of code when this.endpost() is called in FormLetterJournalPost class (method : Post()), the debugger doesnt enter the code and exits directly to the last braces of post() method.
i kept debugger on end post method too but that doesnt work. No further customization have been done on same method, hence breaking up on the standard code itself
i tried full build, usage data clearing, iis reset, database sync, services restart, would like some expert advice in field of d365 Finance and operations