The changing back of appointments is probably because you have more than one relationship to that folder and the settings are not doing what you want them to do.
It also may be that your phones may not have the updated version of their software, Exchange may need to be updated, and Add2Exchange may need the latest version.
First let's take a look at your relationships.
Go into the Console and go to Help, and Export your settings (relationships) and send them to firstname.lastname@example.org For security sake, don't post them here, always communicate to Support@diditbetter.com please.
The relationships are set so that the source item wins, probably, and you want to be able to make changes. The settings for bidirectional on edits is Conflict resolution is always Overwrite source, and for Copied resolution; Write changes back to source.
Next , let's avoid sync errors caused by using older MS technology.
Remember, the Add2Exchange Service is at the tip of the flagpole, with Exchange, Windows, SQL, .net and the actual version of Add2Exchange all working in sync (pardon the pun). The version of A2E on the web is certified to work with the current critical service packs in effect at the time. Make sure you have both current. For completeness sake and to help others, use this procedure to get the latest. You seem to already have it. http://support.diditbetter.com/kb/A2E_194.aspx.
Make sure you have the latest Exchange Service packs. For example, at this time, apply Exchange 2007 SP3 rollup 3 V2 and then reboot the Exchange server. Be sure to stop the Add2Exchange Service before you apply them.
Next let's focus on the Smartphone
Some recurring calendar items may not replicate to the smartphone, but Add2Exchange has replicated it to the User's mailbox. If the item is not in the mailbox, then it is outside the date range to replicate and a change in Add2Exchange is necessary. Open the Add2Exchange Console and Global Options and set the recurrence window longer in the past. This is not the most ideal way to solve the problem, because the sync system now will investigate and replicate many items in the past which may not need to be replicated, slows the replication process down and causes longer sync cycles. But it is easy. The better option is to stop the OLD recurring item at the last instance and make a new one more recent. See this link: http://guides.diditbetter.com/a2e-guide/recurring_appointments.htm
If the item is in Outlook in the destination folder, but does not appear on the phone, there are settings on the phone to change to capture all the older items. The smart phones are being subsidized by the carriers. The carriers are releasing the devices with settings to minimize the data flow and thus traffic on their networks. The smartphone data settings are also minimized to cost less to a user in a roaming data environment where the data transfer may cost more and doing this certainly avoids billing disputes.
If you want the items to sync to the smartphone, you will need to make some changes to the settings on the phone. In this case, Add2Exchange or Add2Outlook is synchronizing the information to the destination mailbox, but the recurring item is in the past and is not being caught by the settings on the Iphone, droid or BB.
Make sure the IPhone has the latest using ITunes. Back it up first.
Then check settings on the Iphone, verify these settings:
go to the affected iPhone
Open the smartphone settings
Select Mail, Contacts and Calendars
Go all the way to the bottom and check the Calendar options make sure the default calendar is selected
Slide to the settings of the Sync
Select how long, and select all events
If an item is not being changed or it is not showing up at the right time (an hour or two before or after, go back and check the setting for the time zone.
Then after this step, go to the top and Pick the account
Make sure the sync is on for that folder type, which is probably is on your phone.
Once we sanitize your relationships and confirm these settings, things will stop bouncing around and you will have consistent replication again.