Please setup the proper icons and shapes for the error events. The attachments shows how each icon should look like and below are pointers to files that contains the icons and shapes.
Thanks!

Icon files:

https://github.com/kiegroup/kie-wb-common/blob/master/kie-wb-common-stunner/kie-wb-common-stunner-sets/kie-wb-common-stunner-bpmn/kie-wb-common-stunner-bpmn-client/src/main/resources/org/kie/workbench/common/stunner/bpmn/client/resources/images/icons/event/event-start-error.svg

https://github.com/kiegroup/kie-wb-common/blob/master/kie-wb-common-stunner/kie-wb-common-stunner-sets/kie-wb-common-stunner-bpmn/kie-wb-common-stunner-bpmn-client/src/main/resources/org/kie/workbench/common/stunner/bpmn/client/resources/images/icons/event/event-intermediate-error.svg

https://github.com/kiegroup/kie-wb-common/blob/master/kie-wb-common-stunner/kie-wb-common-stunner-sets/kie-wb-common-stunner-bpmn/kie-wb-common-stunner-bpmn-client/src/main/resources/org/kie/workbench/common/stunner/bpmn/client/resources/images/icons/event/event-end-error.svg

Shapes definition file:

https://github.com/kiegroup/kie-wb-common/blob/master/kie-wb-common-stunner/kie-wb-common-stunner-sets/kie-wb-common-stunner-bpmn/kie-wb-common-stunner-bpmn-client/src/main/resources/org/kie/workbench/common/stunner/bpmn/client/resources/images/shapes/event-all.svg

https://github.com/kiegroup/kie-wb-common/blob/master/kie-wb-common-stunner/kie-wb-common-stunner-sets/kie-wb-common-stunner-bpmn/kie-wb-common-stunner-bpmn-client/src/main/resources/org/kie/workbench/common/stunner/bpmn/client/resources/images/shapes/bpmn-shapes.css