iPhone 4s suddenly will not charge and home button unresponsive

I have an old spare iPhone 4s, which has been connected to an iHome speaker since the time I upgraded to a new phone years ago. Being that it was always docked with the iHome, its battery charge should have been at 100% at all times. Yet, a couple weeks ago, I saw where the percentage had dropped from one day to the next. In inspecting this, I also found that the home button has stopped working. I can turn the device back on by swapping in another iPhone 4s’s charged battery. While powered on, I can observe that the home button remains unresponsive and that the iPhone will not react to being connected to a power source. I have swapped out cables in the mix of this, with no improvement (same cables power the other 4s I have just fine). Any easy fixes to explore, or is this unit ready for the recycle pit?