Um, shouldn't the calibration program start automatically after reset/power loss?
I was an m100 owner about 20 years ago, but I can't remember starting the calibration program by hand. 🤷‍♂️

No, unfortunately it doesn't start and I don't know how to calibrate the handheld.

Is the stylus genuine or generic?

This does matter and yes should work with good stylus pre-calibration stage if the quality of stylus is good one, which apparently yours is not.

Cheers,

Yes, the stylus is original.

I got a M105 and if I do a hard reset I always get the calibration screen. Hard reset: simultaneously holding down the power button while also pressing the reset button on the back with a paper clip.

Let me explain the situation step by step. Yes, if I do a full reset the problem doesn’t happen. Maybe I forgot to mention that the problem only occurs when I connect the PDA to the PC and sync the data. After everything is synced, (only the first time) the handheld restarts. After it has restarted, it contains all the data and documents that were on the PC, but the accuracy of the stylus becomes very poor and needs a new calibration. However, I can’t do that because since it’s not calibrated well, I can’t tap on the “welcome” icon, which lets me calibrate the tip again.
Furthermore:
I found out that it’s a language issue. Basically, this problem happens when I set the handheld to Italian, but if I set it to English, the problem is less severe, meaning that I can click “welcome” and calibrate the stylus properly. Unfortunately, I can’t set it to Italian. I wonder if there is a way to change the language of the device without resetting it. I searched in the options but I couldn’t find anything.

Hi, I have an idea, but it's a bit dangerous.
Maybe the m100 has an older release of PalmOS installed.
I vaguely there were a few smaller upgrades for the m100.

Speaking under correction, though.
I've switched to a Handspring Visor soon after, which had the latest PalmOS at the time.
So my memory isn't correct, maybe.

Edit: Just checked. The m100 got Palm OS 3.5.1, at least. In German, at least.
This apparently was a response by Palm torwards Handspring's Visor.

https://www.klawitter.de/palm/allgemein.html

Edit: It might be that the m100 has a ROM (no Flash).
So merely small updates can be done (pazches installed in RAM).

I confirm that the Palm OS version is 3.5.1. While trying to solve the problem, an idea came to mind. I bought a folding keyboard on ebay, still sealed, for my Palm. Maybe this will solve the problem. Instead of using the stylus to go to “welcome” and recalibrate the nib, I will use the keyboard to launch the calibration application.

That's quite a possibility, yes. PalmOS 3.5 should already support the concept of "arrow keys".
Some Palm models had a few physical buttons that could be used as "d-pad" by games, for example.

Let's hope it works. It will take almost a month before it arrives in Italy. I'll let you know then!

EDIT:
I found this software:
https://palmdb.net/app/digifix
I installed it, but at the soft reset instead of starting the calibration it starts "preferences" rather strangely.
Do you know this program? And how to make it work well?