Magento 2.3.4 - at checkout: Something went wrong with your request. Please try again later

Question

For some wired reason my Magento stopped working at checkout. As soon as I go to checkout I get that error. Shipping is not calculated anymore in the frontend, but it works in the admin when taking orders by phone.

Anyone seen that error?

Edit: if you want to see the error go to: www.gmsoap.com

To answer the first comment, this is the output from the system.log

[2020-05-01 17:50:25] main.INFO: Broken reference: the 'catalog.compare.sidebar' element cannot be added as child to 'sidebar.additional', because the latter doesn't exist [] []
[2020-05-01 17:50:25] main.INFO: Broken reference: the 'sale.reorder.sidebar' element cannot be added as child to 'sidebar.additional', because the latter doesn't exist [] []
[2020-05-01 17:50:25] main.INFO: Broken reference: the 'wishlist_sidebar' element cannot be added as child to 'sidebar.additional', because the latter doesn't exist [] []
[2020-05-01 17:50:25] main.INFO: Broken reference: the 'custom.sidebar.content' element cannot be added as child to 'sidebar.additional', because the latter doesn't exist [] []
[2020-05-01 17:50:25] main.INFO: Broken reference: the 'author-link' element cannot be added as child to 'customer_account_navigation', because the latter doesn't exist [] []
[2020-05-01 17:50:25] main.INFO: Broken reference: the 'custom_info.order.success' element cannot be added as child to 'order.success.additional.info', because the latter doesn't exist [] []
[2020-05-01 17:50:25] main.INFO: Broken reference: the 'minicart' tries to reorder itself towards 'logo', but their parents are different: 'header-wrapper' and 'header' respectively. [] []
[2020-05-01 17:50:25] main.INFO: Broken reference: the 'custom.sidebar.content' tries to reorder itself towards '', but their parents are different: 'sidebar.additional' and '' respectively. [] []
[2020-05-01 17:50:25] main.INFO: Broken reference: the 'custom_info.order.success' tries to reorder itself towards '', but their parents are different: 'order.success.additional.info' and '' respectively. [] []
[2020-05-01 17:50:28] main.INFO: Broken reference: the 'mgs.instant.search.autocomplete' element cannot be added as child to 'top.search', because the latter doesn't exist [] []
[2020-05-01 17:50:29] main.INFO: Broken reference: the 'mgs.instant.search.autocomplete' element cannot be added as child to 'top.search', because the latter doesn't exist [] []
[2020-05-01 17:50:29] main.ERROR: Topic "inventory.source.items.cleanup" is not configured. [] []
[2020-05-01 17:50:29] main.ERROR: Topic "inventory.source.items.cleanup" is not configured. [] []

Answer 1

later today I realized something wired with one of the orders I had. Upon clicking it, I got a major php error (exception). I could not open the order. It looked like that Stripe, my payment processor extensions, could not find some webhooks in the DB.

So I compared the webhooks in the API records from stripe and was able to manually enter the missing record. After that, all was working fine all of a sudden. If I would have not clicked that order, I would never have been able to figure that one out. Wired thing, but problem is solved!