I keep forgetting this, cause I do development in other languages and frameworks as well, and nothing in the LANSA editor stops me. But WAM command handlers must not have a name of more than 8 characters.
Or rather, it can and it will work, but then when you try to set it up in the VLF, you, again without warning, enter the more-than-8 character name and lo and behold, you end up with errors on your site.
Instead, a command handler named, for example, CH_FAKKOP, should be referenced in the VLF by the first 8 characters, CH_FAKKO, even though the WAM component is 9 characters.
Edit: This also applies to the WAM name in XSLT, like
<xsl:with-param name="on_change_wrname" select="'UHandleEvent'" /> <xsl:with-param name="on_change_wamname" select="'CH_FAKKO'" />