Papar D1 FDC

I generally do not collect first day covers as by implication they are philatelic in origin. However, I have a weakness for this cancellation. Its imperfection and distorted nature makes it all the more appealing. 

This is a FDC of the 1949 UPU issue showing a full set of the stamps cancelled at Papar. I do not like large empty spaces on a cover and the the front part of the cover is nicely filled with addresses both in English and Chinese.

A few more examples of this cancellation on piece and stamps. I have trying to work out whether there were different periods when the postmark was in violet and black and concluded that they were used concurrently. 

Another mystery is why the two rings of this cancellation are distorted. One view was that the wrong type of cleaner was used on the rubber temporary handstamp. But then it would have been perfect to start with like the similar ones from Keningau and Semporna. But I have not seen an non distorted cancellation of Papar D1. Was the wrong sort of rubber used which did not set properly? 

The bottom two examples are intriguing. They looked damaged but does not appear distorted with wavy lines. This implies that a different handstamp was used giving a Papar D1 type 2 cancellation.