I found many people getting bitten by this: google for “wordpress x gets replaced by multiplication”.
So I think, if it is not a link, but just text, wordpress messes around.
Try this, in events-manager.php, around line 1207 (where #_EVENTIMAGETHUMBURL gets parsed), remove the lines that say:
if ($target == "html") {
$replacement = apply_filters('eme_general', $replacement);
} elseif ($target == "rss") {
$replacement = apply_filters('eme_general_rss', $replacement);
} else {
$replacement = apply_filters('eme_text', $replacement);
}
If it works, I’ll remove these for other URL placeholders too