For example Poetry en->es:
Cxserver response is
TypeError: Cannot read property 'attributes' of null
at Parser.onopentag (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/src/lib/lineardoc/Parser.js:132:29)
at emit (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/node_modules/sax/lib/sax.js:640:35)
at emitNode (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/node_modules/sax/lib/sax.js:645:5)
at openTag (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/node_modules/sax/lib/sax.js:841:5)
at Parser.write (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/node_modules/sax/lib/sax.js:1404:13)
at Apertium.buildSourceDoc (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/src/lib/mt/MTClient.js:368:10)
at Apertium.translateHtml (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/src/lib/mt/MTClient.js:80:8)
at Apertium.translate (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/src/lib/mt/MTClient.js:43:16)
at MWReference.<anonymous> (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/src/lib/translationunits/MWReference.js:48:60)
at next (native)
at resume (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/src/lib/util.js:277:21)
at resumeNext (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/src/lib/util.js:287:26)
at /srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/src/lib/util.js:289:3
at spawn (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/src/lib/util.js:272:9)
at MWReference.adapt (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/src/lib/util.js:301:10)
at Doc.<anonymous> (/srv/deployment/cxserver/deploy-cache/revs/3cb9a219599c91befba2a8adc581a6a32def0595/src/lib/lineardoc/Doc.js:270:36)