user6: I tried to merge plant into botany using the mod-only tag merge tool and I get an "Oops! Something Bad Happened!". 
I tried the tool on Skeptics and it worked fine. Checking or unchecking the "also create a synonym" option does not change anything, I always get the error.

user122: The problem here is the proposed synonym from botany to plant; if you delete that - it should work OK.

6: <p>I tried to merge <a href="https://biology.stackexchange.com/questions/tagged/plant" class="post-tag" title="show questions tagged &#39;plant&#39;" rel="tag">plant</a> into <a href="https://biology.stackexchange.com/questions/tagged/botany" class="post-tag" title="show questions tagged &#39;botany&#39;" rel="tag">botany</a> using the mod-only tag merge tool and I get an "Oops! Something Bad Happened!". </p>

<p>I tried the tool on Skeptics and it worked fine. Checking or unchecking the "also create a synonym" option does not change anything, I always get the error.</p>
 122: <p>The problem here is the <a href="https://biology.stackexchange.com/tags/synonyms">proposed synonym</a> from <a href="https://biology.stackexchange.com/questions/tagged/botany" class="post-tag" title="show questions tagged &#39;botany&#39;" rel="tag">botany</a> to <a href="https://biology.stackexchange.com/questions/tagged/plant" class="post-tag" title="show questions tagged &#39;plant&#39;" rel="tag">plant</a>; if you delete that - it should work OK.</p>
