While upgrading to 6.4, we ran pattern detector report and got below lines for ECU category. Is there any reference to fix this issue?
Cross-boundary resource type usage of internal marked path /libs/cq/gui/components/projects/admin/projectteam referenced at /apps/cq/core/content/projects/gadgets/xtrftranslationprojectsummary/jcr:content/content/items/form/items/fixedcolumns/items/column2/items/tabs/items/tab1/items/projectmembers
One more:
Cross-boundary resource type usage of internal marked path /libs/cq/gui/components/projects/admin/wizard/properties/thumbnail referenced at /apps/cq/core/content/projects/wizard/xtrftranslationproject/defaultproject/items/column1/items/cover
As per the official documentation, this means that your custom code uses components that are considered internal and are not part of the API. Both errors say you referenced them so we're looking at simple use (rather than an overlay or inheritance based on sling:resourceSuperType). You just have a couple resources with the sling:resourceType values belonging to internal components whose use in this context is not something that's officially supported or tested.
They may break at some point when you upgrade to a newer version of AEM or try to apply a hotfix.
The best way to go forward would be to stop using them and replace them with other components that are considered public and therefore supported. If no suitable replacement is available, you should consider replacing them with custom code that you control.
I'm not familiar with either cq/gui/components/projects/admin/projectteam or cq/gui/components/projects/admin/wizard/properties/thumbnail so I can't recommend any replacements. Any potential replacement should have the mixin type of either granite:PublicArea (can be used, overlaid or inherited), granite:AbstractArea (can be inherited but not overlaid or used directly) or granite:FinalArea (can be used but not inherited).