Bob, this is Evo. No separate cache file for chunks.
If the database were corrupted, it wouldn't be able to load the tpl from the database into the Manager's form field. It could be a problem with the site cache file; all chunks and snippets are taken from there for use during parsing, but it's odd that only the forms should be affected. The timing also makes me wonder if it's something to do with a server configuration having to do with limits on the email being sent; but in that case why would saving the chunk cause it to begin working again?
Here's what I would do, in any case.
Upgrade the eForm to 1.4.4.7 (you can get it here
https://forums.modx.com/thread/47493/a-new-version-of-eform-with-built-in-smtp-beta-for-testing?page=3#dis-post-274564 or here
https://github.com/yama/eform ) and use an external config file. The external config file is just a .php file, so you can define the template code (as well as all of the other eform parameters) in the file as a PHP variable:
[!eForm? &config=`contact`!]
The filename would be the first part of a filename such as 'contact.config.php' in the assets/snippets/eform/configs directory.
$tpl = '
<span style="color:red">[+validationmessage+]</span>
<form id="ContactForm" method="post" action="[~[*id*]~]" enctype="multipart/form-data">
<fieldset id="info">
<input type="hidden" name="formid" value="ContactForm" />
<label for="cfName">Name: </label>
<input tabindex="1" name="name" id="cfName" class="text" type="text" eform="Your Name::1:" />
<input tabindex="50" type="text" name="Last__Name" id="LastName" size=30 autocomplete="off" eform="LastName::0" />
<label for="cfEmail">Email: </label>
<input tabindex="2" name="email" id="cfEmail" class="text" type="text" eform="Email Address:email:1" />
<label for="cfUrl">Website: </label>
<input tabindex="2" name="url" id="cfUrl" class="text" type="text" eform="Website::0" />
</fieldset>
<fieldset id="message">
<label for="cfMessage">Message: </label>
<textarea tabindex="3" name="message" id="cfMessage" rows="4" cols="20" eform="Message::1"></textarea>
<input tabindex="4" type="submit" name="contact" id="cfContact" class="button" value="Send Message" />
</fieldset>
</form>
';
The zip file contains an example config file in the configs directory.
☆ A M B ☆