Canon 1.4x III causing shutter lag?

I'm in the field in Montana with a new Canon 1.4x III. I'm pairing it with a 300 F4 L IS. Across multiple camera bodies and numerous, varied settings, I notice I'm either getting shutter lag or what sounds like shutter lag. It's totally random, but you can definitely tell.

I bought the TC new from Amazon, but it didn't come with the soft pouch. Images seem okay, not much different from my Canon 1.4 II.

I'm wondering if this is standard behavior with the new 1.4x III?