I am guessing you have been using signlab for some time and this is a NEW problem?
I would try using a different font from a different file type, source and repeat the same process. See if it still happens.
By this I mean, when you go to select a font you will see little icons. These “sometimes” indicate the source of the font. Like, if it is a signlab font, a windows font that comes with your computer, or Corel or Adobe if you have another graphics package on your computer. (see attached image)
If you on-screen manually digitise a shape, you will see a minimum amount of nodes appear.
But if you make that same shape “a path” the software will find every little anomaly in the artwork and add and replace it with extra nodes. Sometimes hundreds, depending on how good the tracing process was. based on this, “I am wondering” if the font you have chosen appears clean but when converted, the software is finding errors in the path and adding lots of new nodes.
The two parts that have me confused and doubting what I have just said is the “actual shape” of the font should not distort at all and no matter if you scale up or down, it should not get worse if you are using a vector.
I had a graphic designer a while back, and they were forever faffing around with their settings and preferences in Signlab. In doing so, they created a problem that every time they used certain fonts from certain families, the font would corrupt and look terrible. i.e. the letter “O” would look the shape of a 50p piece! anyway, from memory I just did a factory reset of the software or uninstalled it and reinstalled it and it fixed the issue. I am only mentioning this on the off chance you have changed something without realising it.