Check if this helps In Mail question mark is coming in place of special characters Did you try to reproduce this issue with an updated version of acs commons?

I haven't seen any papers on SPA-ecomm integration as a recommended path. In my mind, I'm not sure of the benefits of SPA owning it rather than AEM with GraphQL route. I'd probably do more research later.Alternate route per Adobe's own CIF  --  Integrations Integration patternThe AEM Venia Store fro...

A solution would be to write a custom exporter based on your use caseAdobe Experience Manager Help | Developing Sling Model Exporters in AEM Adobe Experience Manager Help | Understanding Sling Model Exporters in AEM

You may check with "LDAP" or "Login" keyword in code/config files in your repo or under /apps/settings or in /system/console/configMgr

Did you enable LDAP or external login integration or similar feature in the setup where you see this issue? If yes then that could be a pointer to debug further..

you mentioned that it happens only when you switch between code branches - can't you revert/fix your code? You probably have a wrong config that overwrites /apps/settings or authentication configs?

check if this helps - AEM 6.3 author instance returns 403 for clientlibs and j_security_check

Did you get a chance to check ACS AEM Samples -  Sling Event HandlerSling Event Handler (with Immediate Job Execution)You may swap SCR annotations with OSGI annotations. Refer - Re: Difference between SCR as well as R6 Annotation​ for examples

The package might have already been installed/errored out. Check console logs/error.log for more detailsAlternatively, try this How to install CRX packages automatically on server startup

what version of JRE do you use? Make sure that it is supported: Technical Requirements