Just want to make sure we are referring to the same motors as I s eem to recall some people refer to the sizes in one way and some in another. To me (rightly or wrongly!) a 1015 and a 1020 differ in their length and speed, not body width?
This is what I call a 1015
http://motorbogies.com/index.php?main_page=product_info&cPath=2&products_id=12
And a 1020
http://motorbogies.com/index.php?main_page=product_info&cPath=2&products_id=172
Both have small eyelet terminals. The ones I understand to be not as reliable are this size:
https://www.ebay.co.uk/itm/125000181982
With the contacts a strip of phosphor bronze rather than eyelets on a stepped in section of the motor housing?