By the way have you been reading the MDL-33890 about the Drag n Drop issue with custom blocks in M2.3?
These a fix for ../moodle/lib/yui/blocks/blocks.js which I have attached for you to try in Moodle 2.3
The code you need to add to your block reagion in your layout file is as follows...an amended example from your Strawberry theme...
<div id="blocktopleft" class="block-region">
<div class="region-content">
<?php // echo $OUTPUT->blocks_for_region('block-top-left') ?>
</div>
</div>
You have to add class="block-region" to your div id container as well as region-content that wraps the block.