Printing problem

We have a Tally MT6140 dot matrix printer which is used to print payslips.We are experiencing a printing problem where it omits a line of characters and doesn’t print the date correctly. I ran a character set configuration page and noticed that it prints a series of numbers and then alpha numbers in US, English,German etc… This row is 96 characters long and it misses the 78th character and starts again on the 79th e.g 0123456789ABC EF0123456789ABCDEF ETC………..if you notice, “D” is missing from the row and I need to know how I can resolve this? Is it a Software or Hardware problem, Is it the Hammers? Is it in the Configuration?
Many thanks