To preface; this is not a fix, but a work-around based on the testing i've done with multiple romanceable npc's (excluding merfolk). Current platform i've tested: PC/Steam V.1-184 (pre recent hotfix). Information may differ with different platforms, so if you have any additional information to add in or out of the current platform i've mentioned, please do share it. I write this in hopes it can be of help to both players and devs in pinpointing the 10 heart events not triggering.
Important Note: for cross checking, you may look up the 1.0 Non-Spoiler NPC Romance Guide, Official and Fandom Wiki's provided in the Community Guidelines/Information Directory. Should any of what i mentioned still not working, please refer to the Coral-Bugs-Report 🙏
Tested 10 Hearts NPC's in the clear:
Bachelor: Surya, Rafael, Scott, Pablo, Luke, Ben, Mark, Noah, Wakuu
Bachelorette: Aaliyah, Alice, Macy, Nina, Eva, Leah, Yuri, Suki, Lily, Zarah
Yet to be tested:
Theo, Kenny, Raj, Chaem, Millie
Confirmed bugged NPC 10 Hearts (based on personal testing):
Millie (no invitation letter, per PC 1-184)
10 Hearts not triggering causes:
1. Reaching 10 Hearts in Winter : some npcs have Winter season restriction. However, avoid reaching 10 hearts in Winter just in case.
2. Reaching 10 Hearts via Temple Offering : currently the game doesn't seem to recognize npc maxed out via temple offering. Do keep in mind when trying to work on temple offerings. Learned this the hard way with Mark, Theo, and Yuri.
3. Same week as Spooky Festival : possible that the spooky decor conflicts events within town and beach area. Events will proceed normally after Spooky Festival, excluding the Winter restriction for 10 hearts. Heart event can still trigger if it's outside of town and beach area (forest/lake) during Spooky week.
Workarounds to try:
- Gift twice a week, interact everyday;
- Reach other npc 10 hearts (currently no repercussion for polyamorous)