Problems with join on sorted key column but linux says "not in expected order"

File 1. Column1=old_id; Column2=snp_info (50 000 integers, so too large to show, containts 0,1,2,5 -> i.e., 020112202010511)

80024979
80024987
80025141
80107980
80922131
81666414
81667586
87021127
87028460
2010112924
2010115513
2010186050

File 2. Column1=old_id; Column2=new_id.

79931168 58155
79944336 58190
79969242 72833
80107980 58150
80922131 58109
2010112924 96821
2010115513 80604
2010186050 47254
2010198857 90190
2010229173 96927
2010229330 67548

I am trying to join on column 1 which was sorted using sort -k 1n file1 and the same for file2. When joining (in linux) I get the following error:

join: file 2 is not in expected order
join: file 1 is not in expected order.

If I look at the join, this is where it gives the error: ...200000010000000000000000 58150 join: file 2 is not in expected order -> but continues with the next old_id (file1) and their column2 value -> 80922131 1100000020000... ...001000010 58109 -> and then it stops here, that is again with column2 of file1 and column 2 of file 2 (the new_id column I want to put in). I looked at the values, it start giving errors and stop where in file2 column 1 the old_id goes from a value with 8 integers to values of 10 integers. Notice that it is indeed sorted correctly. How do I solve this? What is the cause? Pictures included. Thank you in advance. File 1, column1, (column2 not shown, but = 0101020222015... -> 50 000 integers per id) File 2, column1=old_id, column2=new_id Result1 where it continuous: Result2 where it stops. Any help will be immensely appreciated. Kind regards, Michiel.