The “Error” that you see (Your theme’s template file for displaying Apartment items is missing custom fields) is not an error, but just a notification.
It states, that the template with which your Theme displays the posts to which you attached Some Custom Fields, does not display them.
To display Types Custom Fields usually (if you do not use the rest of Toolset) you will either use the ShortCodes in a Post Body or the API in the templates.
Since the Template right now holds probably no such API the Dashboard tells you that.
However it’s not a “error” per se, and not the reason for the Fatal error that you receive.
The fatal error is due to an expensive process running on the site and running out of memory (this may start in other plugins and end in types).
Related to Types, this can be due for example when you’d use nested ShortCodes or Conditionals – but that is possible only when you use Toolset Views – hence not the issue here.
I suspect rather that the site has either a very large number of fields, repeating field or a very low value assessed for allowed memory size in PHP.
But what as well confuses me is the Folder/File path you mention in the error.
In the fresh download from here there is no such file in that folder, the file is in /types/vendor/toolset/types/embedded/classes/fields.php
The code there gets data for certain field types, so I would check if you have complex fields on those posts which throw errors, and increase the memory limit on the server.
If this issue still persist after, I recommend to check it without any other plugin/theme but Types and Twenty Seventeen.
If that doesn’t solve the issue, we will see how to proceed further, as it’s a little difficult for me to share more details (copy of site, login) here in WordPress forum.
==> If you have the chance to mention what action provoked the issue, or what you did, you could try to revert back to previous stage and I can then try to replicate according your instructions (as of what to do to make it happen)
Let’s hope above tips help to solve the issue.
Usually this is solvable on the server level (increase the memory allowance)
