I didn't realize breadboards were that cumbersome to high AC frequency.
A breadboard has hundreds of intermittent contacts that make poor contact. A soldered joint is much better.
It has rows (of contacts) that have fairly high capacitance between them that is bad at high frequencies. The connecting wires also have high capacitance (coupling?) between them (oscillation?).
The rows of contacts and the long connecting wires have series inductance that is bad at high frequencies and causer oscillation.
Use a breadboard only for DC or for low frequencies.
Should I try and make a PCB and then take the load to the breadboard and into the LED- and LED+ pins of the display or is that still no good?
For 51 years I have used Veroboard (stripboard) for my prototypes and nearly every one was sold because they worked perfectly and looked good.
Of course every joint was excellent because it was soldered.
The strips of perforated copper are cut with a drill bit at a hole so that the same strip can be used again and again and the circuit is compact (short wires).
The strips of copper form half of a pcb, and the components and a few very short jumper wires form the other half of the wiring.
The holes are already drilled and the strips of copper are already there so it is very simple.
I have designed, made and sold hundreds of Veroboard prototypes (some very complicated) and every one worked perfectly.
The first breadboard circuit I made did not work but worked perfectly on Veroboard so I never used a lousy old breadboard again.