Runs about 5 hours before off

Got 2 Tentacles yesterday. Charged both until green light went solid on (100% charge). Turned both units on, synced, flashing green, let run over night expecting approx. 40 hours run time. Ran about 5 hours before both units showed no flashing LEDs. Charged both again, started at charge level one flash, in about 20 minutes charge level was solid (which seems too fast to be a complete charge). Synced both units, flashing green, and ran. Again about 5 hours before LEDs off.

This is nowhere near 40 hours run time. What is going on here?