"Section source is not supported" JS error when enabling PayPal

[codedge]

After enabling PayPal Express as payment method, the following Javascript error appears on all pages:

http://sds-shop.local.dev/customer/section/load/?sections=cart-data&update_section_id=false&_=1503661222518

The mentioned solution in here #6410, to clear the local storage does not help.

Preconditions

1. Magento CE 2.1.8
2. Google Chrome 60.0.3112.101

Steps to reproduce

1. Configure and enable PayPal Express
2. Put product in to cart
3. Go to checkout
4. Cancel and go back to homepage
5. Error appears.

Expected result

The AJAX call to http://sds-shop.local.dev/customer/section/load/?sections=cart-data&update_section_id=false&_=1503661222518 should work and not resulting in a Javascript error.

Actual result

The console in Google Chrome shows an error.
AJAx Request fails with error 400: http://sds-shop.local.dev/customer/section/load/?sections=cart-data&update_section_id=false&_=1503661222518

Uncaught Error: [object Object]

Response: {"message":""cart-data" section source is not supported."}

[orlangur]

Try to check contents of this response in Network tab and records in var/log of your Magento instance.

[codedge]

@orlangur The response displayed in the Network tab is {"message":""cart-data" section source is not supported."} - as I already stated.
Checking var/log/system.log, which is the only error log created after deleting everything in var/log, there is nothing regarding this issue.

[erfanimani]

I'm also having this issue, except I don't have Paypal enabled. I'm not sure where it comes from, whether it's something I did or a third party extension.

Honestly, it's a confusing message and I'm having trouble debugging it..

edit: actually, I can't reproduce this in incognito.. never mind.

[sinamiandashti]

same here
happening to me
not related to paypal
we dont know what is it

[eInyzant]

same problem here on magento 2.1.9
I tried this solution : #6410 (comment)
It works well until I switch from my french store to the english store... It seems to be cache/storage related.

[jzembala]

I also encountered this issue.
The only thing I found is that Magento checkout cache uses this section name and when it should be deleted there is null value set (but record still exists).

As I see totals-processor uses this key.

[magento-engcom-team]

@codedge, thank you for your report.
The issue is already fixed in 2.2.0