Insufficient / Unstable Current from LM2678SX-5.0

I have an application where I'm down-converting 24V DC to 5V DC to power a 5V load that can draw up to 4A. I selected the LM2678SX-5.0 due to the simplicity and implemented the reference circuit in its respective datasheet.

Unfortunately, while I do observe a 5V output I see either an insufficient / unstable current output. As soon as my device draws any significant power, the voltage drops to 0 and then the device resets and with a lower current draw the output voltage again rises to 5V. This was analyzed using a scope. I know that the load is not more than 5A as I have confirmed this on a variable DC PSU plugged directly into the device and I have used AC adapters with less than 4A of output. I have also tried several 5V devices and observed similar issues. I have also used OTS DCDC convertor solutions connected to the same 24V input and have observed the load functioning properly so I know that the 24V input PSU is sufficient (actually way more than sufficient as it is 150W).

It's worth mentioning that I tried to secure the exact components as listed in the datasheet but ran into sourcing issues (parts not stock items, no longer available, etc.) and was forced to select components with the same requisite characteristics.

In all my testing, the only thing that appeared to have any effect was the inductor. The output appears to be better (device stays on longer) when I use a 22uH inductor over a 47uH inductor. This is strange though as from what I have read, bigger is better in terms of inductors. Both inductors I have used have had the same resonant frequency so that shouldn't be dictating the change in performance.

I've been racking my head over this one- if anyone has any suggestions about what to look at I would greatly appreciate it. My circuit is the reference schematic in the datasheet here (www.ti.com/.../lm2678.pdf) and my BOM is below: