WooCommerce (4.8.0) WordPress (5.6) ACF PRO 5.9.[23] Conflict: not saving the SKU value for Variable Product

Prerequisites (mark completed items with an [x]):

[X] I have have carried out troubleshooting steps and I believe I have found a bug.
[X] I have searched for similar bugs in both open and closed issues and cannot find a duplicate.
Describe the bug
Problem: SKU value on main variable product is not shown, after adding a value followed by successful update message.
The field is blank - no value is shown.

More details:
Update of each SKU value in theis product variations succeeds.

Steps to reproduce the bug (We need to be able to reproduce the bug in order to fix it.)
Steps to reproduce the bug:

Generate a variable product with 2-3 variations
Modify the SKU value & Update (save it)
After message that update was successful
SKU filed is emapty
I am using WooCommerce (4.8.0) WordPress (5.6)

Turned off all plugins, but Woocommerce - did not help.

Replaced theme to default 2020 - did not help.

Debug is ON and clean on all tests & No JS issues reported.

Any idea what might be the issue? or how to debug it?

Isolating the problem (mark completed items with an [x]):

I have deactivated other plugins and confirmed this bug occurs when only WooCommerce plugin is active.
This bug happens with a default WordPress theme active, or Storefront.
I can reproduce this bug consistently using the steps above.
WordPress Environment

No source file or test is identified in the issue. First reproduce the problem with WooCommerce 4.8.0, WordPress 5.6, and ACF PRO 5.9.2 or 5.9.3 using a variable product with two or three variations; done means the main product SKU remains visible after saving, while variation SKUs continue to update.