Using a database of 33,788 records, I split the Employee Name field into First Name and Last Name. Employee Name was split after first space with surrounding blanks stripped. Upon clicking Split, no movement - except the active column moved to the right. Scrolling the Data Sheet makes all the data disappear and freezes the Data Sheet - can not close it. All other PanX menus seem to work. Had to quit PanX to get Data Sheet window to close. Upon reopening this same database, the field is split correctly.
Also, in the Split pane, the preview of the first 250 records does not display without data drop out - scrolling the preview list makes some of the records disappear or records are blank.
I have replicated this behavior in the same database and in a database with 25 records, so number of records does not seem to be an issue.
iMac running MacOS 10.10.5.