Low voltage LEDs fluctuate from full to half to off and repeat
I see several problems.
Provenance
A quick google of the terms you gave lead me to a quality power supply, but straight to eBay/Amazon for the lights proper. The Amazon items were &quot;cheap Cheese junk&quot; that lacked even a UL listing to assure product quality.
The cheapie lights also came with &quot;pierce the wire&quot; type connectors that jab a spike into the wires.  These fail very quickly.  These appear to be unique to the halls of China; I don't see any &quot;spike&quot; connectors from any reputable vendors.
Voltage drop
I checked a voltage drop calculator for what happens to 12V at 8 amps over 22 feet of #16 wire.    It says you get 1.41 volts of drop.  Leaving 10.59 volts at lamp 1.
Now assuming it's 8' from lamp 1 to lamp 2, that wire needs to carry 7 amps. Plugging that in, it's telling me 0.45 volts; totalling 1.86V so far.  So at lamp 2, voltage is 10.14V.  Continuing to assume 8' between lamps...
Wire from lamp 2-3 carries 6A, dropping 0.39V.  Lamp 3 sees 9.75V.
Wire from lamp 3-4 carries 5A, dropping 0.32V.  Lamp 4 sees 9.43V.
Wire from lamp 4-5 carries 4A, dropping 0.26V.  Lamp 5 sees 9.17V.
Wire from lamp 5-6 carries 3A, dropping 0.19V.  Lamp 6 sees 8.98V.
Wire from lamp 6-7 carries 2A, dropping 0.13V.  Lamp 7 sees 8.85V.
Wire from lamp 7-8 carries 1A, dropping 0.06V.  Lamp 8 sees 8.79V.
A bump in wire size to something like #12 would probably make a big difference here.  Alternately, going with smaller lights would work.  A top rate kit made by Volt includes #14 wire for 5W lamps.