Ugh... if versionNumber is correct this sould NOT happen. Version strings are otherwise compared, this may be a bug, will check.
Is this a nostr:nprofile1qqs83nn04fezvsu89p8xg7axjwye2u67errat3dx2um725fs7qnrqlgzqtdq0 issue or bad versionNumber in the .apk? 
Discussion
I double checked and the numbers were changed: https://github.com/RoboSats/robosats/commit/69517c55d6ebdc8567a44f725a18b35f34b8910c#diff-b32e9c9736efe96d6fb19cba5145eac8899326f11b9d85edbc036f2ca1474c07R153
Can I somehow help?
nostr:nprofile1qqsyx53h3h7ec4fwlspjq0kqec5gv54t7rc48xdtq6q4y94wsw4fnjqprdmhxue69uhkummnw3ezuumpw3ehgunpd35kztnrdakj7qghwaehxw309aex2mrp0yhrq7rrdpshgtnrdakj7qg4waehxw309aex2mrp0yhxgctdw4eju6t09uhgml9t the parsed version codes are 7 (for 0.7.3-alpha) and 8 (for 0.7.4-alpha) but when installed 0.7.3-alpha reports version code 7003
So 8 < 7003 and shows as downgrade.
I need to dive into this but if you have any pointers let me know
It's a mix up of universal and arm64-v8 version codes. I don't understand this convention of using different code ranges for each.
I noticed your zapstore.yaml includes the universal APK. Can you start publishing arm64-v8 only? Zapstore does not support any other Android architecture, and the APK is way lighter
Okay I'll need check it for the next version, thanks!
That's weird, this is what I get on my device, is there any other place I can check this?
https://nostr.download/2622bf496f4808d85cda3c5d30f2aea49abeb118ebbdbe475b43eaeaae106407.webp