Duplicate custom field blocks on open case
It doesn't actually display twice, but this is interesting:
https://github.com/civicrm/civicrm-core/blob/5.18.4/templates/CRM/Case/Form/Case.tpl#L79-L84
{if $groupTree}
<tr>
<td colspan="2">{include file="CRM/Custom/Form/CustomData.tpl"}</td>
</tr>
{/if}
https://github.com/civicrm/civicrm-core/blob/5.18.4/templates/CRM/Case/Form/Case.tpl#L116-L120
<tr class="crm-case-form-block-custom_data">
<td colspan="2">
{include file="CRM/common/customDataBlock.tpl"}
</td>
</tr>
I guess the question is should the custom fields be near the bottom or top? The problem with top is that if they are specific to a certain case type, then the dropdown where you select the type appears AFTER the custom fields, which is kind of nonstandard and feels wrong. Usually fields that only appear when you make a specific choice appear below or beside the controlling field.
What's also weird is it seems to be inconsistent across sites as to which one displays, but is consistent within a given site. That seems strange. Or not.
Also not sure yet if the groupTree check is needed. The bottom one seems to be more standard.