The pax shows "redial in

You have to be in the fax screen and find your User install or Initial settings screen. Redial can be set there. There's a default setting that I think you can set to "0" redials. I haven't had that manual for a long time.

If the line is busy on the other end, your machine will put it in redial state and will try again. However, the redial function will depend on the setting how many try it will make. If the setting is 2 as an example, it will redial twice only and if it is still a failure it will treat the transaction as "NO" or "NG". You can check this in the transaction list of your machine. As you said, there are numerous complaint, check if the complaint is with the same receipient, if so most probably the end machine is having some problem. If from different destination please have your machine checked by the local service provider.

is that a fax error code?
well here is the description for error 634:

Redial count over with no
response, or busy tone was not
detected.
Note:
U.S.A., and Canadian models
will redial only once if a busy
tone is not detected.

this happens when you send fax on an autofax destination.
you may also check your setting for your redial count
that's it :)

It's been a long time since I have used Panasonic analog phones, but the redial function in them used to be mechanical. It dialed 15 times with a 45 second pause between attempts. The key was, it expected you to pick up the handset, cancelling the redial if you got an answer.
If you got an answer and didn't do anything, it hung up and redialed again until you picked up the handset!

Could that be what your system is doing?

Carl

Yes, scroll through the set-up menus and set Number of Redials

Press the following keys
Function
7
monitor key slowly 4 times
*
1
44
set
clear 2 times
enter 0-15 times redials......I recommend 5 redial tries
set
stop
unplug power cord and replug.

Do you have a DSL or other digital phone line?

That codes says:

"Redial count over with no response
or busy tone was not detected.
Note:
U.S.A. and Canadian models
will redial only once if a busy
tone is not detected."

The number you're dialing was first busy. When it went to redial, it detected no phone signal on the other end. If it happens to only 1 or 2 customers, then it's something to do with their lines and you can't fix that.
If it happens often, then get your phone lines checked out by your phone company, make sure your fax is not sharing the line with another other device and make sure it is not a digital line.
Other than that, you're looking at having to replace the main board in the fax. Which basically means it's time for a new fax machine.

Go into the admin mode or user mode to reset the default settings. Procedure should be in the op manual.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

pleas close the redial option and other number may be busy or finished