Something has brought them back to SI for search IMO. I haven't a clue what but to go back to SI after they ended their extensive searches there makes me really wonder why.
Bear with me, but I do have a relevant point. IMHO, Terri gave LE an account of her day that closely resembles what we read in the e-mail she sent to her friend on June 5. It may vary slightly -- she may have left out some things (Starbucks?) intentionally or unintentionally, but I believe her initial account has been verified to the extent it can be verified. IMHO, LE knows when she couldn't have and when she could've done something to Kyron and disposed of him. For instance, LE knows she was at the FMs, and so IMHO they've ruled out that general time block as the time Terri did whatever she did and in the process they've ruled out that general area. Also, IMHO, at some point the ping results came back on her phone and showed she was near Suavie Island. She accounts for this by saying she was driving K around and trying to soothe her, but LE doesn't buy it. This is the only time period they can't verify, IMHO, but it's not a lot of time. If Terri did something to Kyron, she did it quickly and she disposed of him quickly. She didn't have time to drive 100 miles away or dig a deep grave.
LE believes Terri is guilty and that her phone pinged near Suavie Island at a time when her actions can't be verified continues to lead them there. IMHO, given what LE knows about her day and her whereabouts, she could've ONLY disposed of him on Suavie Island and that is why they continue to revisit the island. Additionally, someone else mentioned that water levels are low right now, and so if Terri disposed of him in the water LE might be able to see any suspicious containers or other remains. IMHO, they didn't go there based on new information, only reexamination of old information.