i experience it takes very long for notes to copy the data, if I select the relevant documents which are collapsed by category, before I can paste it to excel, one time the whole system locked, I ended up have to restart PC twice. It seems much easier if I export to 123.
When you use “copy as table” it has to load everything into memory. So, you could be running into memory problems (too many applications running, not enough RAM to start with, or too large a data set).
When you export it to 123, it writes one line into 123 at a time, using far less memory and relying on processing speed to complete the task quickly.
I would expect that exporting is supposed to be used for large operations while copy and paste is used only for smaller ones. This is not just a Notes issue, but a memory issue (if you copied as much data from Excel to the clipboard, you could run out of memory there that way also).