In one case, an Interactions Upload job was started, then killed, and then an Undo Upload/Download Procedure was run for the killed Interaction Upload, because it added some interactions already. The Interactions Upload of the same file was then processed again later. After the upload, the number solicitations on the sources did not equal the number of interactions that were loaded (assuming the sources started at 0 number solicitations).
When you do an Interactions Upload, it counts up and adds the number solicitations to the Source at the end of the job. Since the Interaction Upload was killed, it had created some interactions but did not update the number solicitations on the Source yet, so they were still 0. When the Undo Upload/Download Procedure was run for the interactions upload to undo the interactions added, the procedure counts how many interactions for each source were added by the upload, then subtracts that amount from the number solicitations on the source. Since it was currently at 0, it ended up with negative number solicitations. Then when the interactions upload is run again, it adds the number of uploaded interactions to the negative number, so you end up with less than the total of uploaded interactions.
Example, of 1000 interactions to be loaded for a source, 50 got loaded before the first job was killed. After the undo, the number solicitations is -50. When the upload is done again and adds the full 1000 interactions, the number solicitations is -50 + 1000 = 950 rather than the full 1000 it should be.
The solution is to manually set the number solicitations on sources to 0 after an undo of a killed interactions upload, or if it is after the second upload already, manually correct set them to the correct amount. If it is too many sources to do manually, you can contact TA support for assistance.