FarmWarDeployer has the following code at line 152: if(econtainer == null && econtainer instanceof Engine) { There's clearly something wrong with that condition.
This has been fixed in trunk and proposed for 6.0.x
This has been fixed in 6.0.x and will be included in 6.0.19 onwards.
Also added to TC 5.5 as r790340. Will be part of 5.5.28.