There were a couple of updates for those older models. Have they been run? The Kindle services updates didn't change the firmware number, so that would be the first thing to try.
How to manually update:
https://www.amazon.com/gp/help/custo...deId=202109170
Where to get the correct update:
https://www.amazon.com/gp/help/custo...MQC26VQQMM8XSW
Make sure to download and transfer the correct bin file for the matching serial number.
Edited to add...I've no idea how the jailbreak affects this.