When importing data into directories, the system hangs and does not import all data

When importing data into directories from a file in XLS format, the system imports data, but every now and then it shows an error and then everything continues to import (when you refresh the page, you can see that records are being added), but it still does not add all the data. That is, for example, there was an XLS file in which there were 9,000 lines and the system imported only 4,500, in some moments it imports less than 4,500, and sometimes more, that is, if there is a file with 100,000 records, it has to be divided into parts and only then imported, this is very inconveniently. It seems that the system is stuck on some server limitations or something else. Can you explain what is wrong and what server settings can affect such import restrictions?