3087670 - Search functionality is not working in Plan Customer Projects app

When trying to search for a project in the Plan Customer projects app, no project is found.

An error is raised in the TREX call:

Return code: 23008

Return text: exception 70023008: Can't create plan for join query

The indexserver trace contains entries similar to the ones below:

XXXX-XX-XX XX:XX:XX e join_eval PlanCreator.cpp(11837) : Found unconnected output with id=XXX
XXXX-XX-XX XX:XX:XX e join_eval PlanCreator.cpp(11852) : Dangling output is created by JEStep2 pop119 (JEStep2)
XXXX-XX-XX XX:XX:XX e join_eval PlanCreator.cpp(02886) : Found unconnected outputs in plan. Please set 'indexserver.ini -> joins -> fail_on_unconnected_outputs = false' and have a closer look by turning on join_eval=info.
XXXX-XX-XX XX:XX:XX e join_eval PlanCreator.cpp(02890) : SqlExecutor at
1: in Diagnose::impl::dumpInfoSelfCtx(ltt::basic_ostream<char, ltt::char_traits<char> >&, bool, bool, bool, bool, bool, bool, unsigned long)+0x65 at Trace.cpp:32 (libhdbbasis.so)
2: in JoinEvaluator::PlanCreator::createPlan(ltt_adp::basic_string<char, ltt::char_traits<char>, ltt::integral_constant<bool, true> >*)::{lambda()#8}::operator()() const [clone .isra.1735] [clone .lto_priv.9893]+0x15e at PlanCreator.cpp:2890 (libhdbcsapi.so)
3: in JoinEvaluator::PlanCreator::createPlan(ltt_adp::basic_string<char, ltt::char_traits<char>, ltt::integral_constant<bool, true> >*)+0x6c1 at PlanCreator.cpp:2890 (libhdbcsapi.so)
4: in TRexAPI::TRexApiSearch::searchJoinIndex(TRexAPI::QueryContext&, TRexAPI::TRexApiSearchTableResult&, ltt_adp::vector<TRexAPI::FSTermAttributeInfo, ltt::integral_constant<bool, true> > const*, ltt_adp::vector<TRexConfig::TableOrView, ltt::integral_constant<bool, true> > const&)+0x31a0 at TRexApiSearch.cpp:9126 (libhdbcsapi.so)
5: in TRexAPI::TRexApiSearch::doSearch(TRexAPI::TRexApiSearchTableResult&)+0x7120 at TRexApiSearch.cpp:5838 (libhdbcsapi.so)
6: in TRexAPI::TRexApiSearch::search(TRexAPI::TRexApiSearchTableResult&)+0x60 at TRexApiSearch.cpp:4932 (libhdbcsapi.so)
7: in TRexAPI::SearchDbslCommand::executeImpl(TrexBase::AsXmlWriter&)+0x847 at TRexApiSearch.cpp:16826 (libhdbcsapi.so)
8: in TREXviaDBSL+0x67b at trex_util.cc:497 (libhdbcswrapper.so)
[...]

SAP S/4HANA Cloud 2108

KBA , CA-CPD-SS , S/4HANA Public Cloud – Professional Service Projects , HAN-DB , SAP HANA Database , Problem