422 error Unprocessable entity INSTRUMENT_DECLINED

Is it possible to look into this a little bit further? I'm running into this issue (the error from OP), but I think the bigger problem that I'm seeing and I'm not sure where to start with debugging it or providing more information for it is that my site is not handling the error at all. Instead it's allowing the order to process with no payments attached.

Order moves into a state for validation and has the look and feel that it was "completed" as a transaction.

Is it possible to look into this a little bit further? I'm running into this issue (the error from OP), but I think the bigger problem that I'm seeing and I'm not sure where to start with debugging it or providing more information for it is that my site is not handling the error at all. Instead it's allowing the order to process with no payments attached.

Order moves into a state for validation and has the look and feel that it was "completed" as a transaction.

I've dug deeper into this.

I’m testing a weird instance where orders can be placed through PayPal but if a specific error is fired off (Insufficient Funds like the one above), the code traceback will go through the process of throwing a PaymentGatewayException however it still proceeds through the code without redirecting back to a previous spot. It actually continues on and places the order, without payment at all.

When it gets to the part of code about redirecting to the $error_step_id, $this->redirectToPrevious() is set to false which I think is where the bug is as well. It should not continue on through the code to where $order->save() is called.

The question I have is… what should my checkout flow look like for Paypal Checkout (Preferred)? Is it possible I have the wrong order of things?

Kinda seems like a bug to me in tthis module, but could it be with commerce itself?

I stumbled upon this error myself.
After reading your comment, I got scared and tested the insufficient funds case.
Fortunately, the order does not complete and the user gets a proper error message and is invited to try again.
FYI: I am using Commerce 2.36, Commerce Paypal 1.4.0, Drupal 9.5.10 with PHP 8.1

I should have followed up. This was due to another module not handling errors properly. This was NOT an issue with commerce_paypal, instead was an issue from commerce_multi_payments and not handling errors well.

So closing this per the comments.