If Arena is outputting something different when outputs are disconnected and reconnected, that's a serious issue, and we'll do everything we can to get a fix out as soon as possible.
To avoid getting in too much speculation though, EDID is a protocol used by monitors to announce information about themselves to the graphic card they are connected to. This information includes resolutions and refresh rates it supports, as well as manufacturing info. This is what defines the options that are available for different resolutions in the screen setup of your operating system.
We do not send out EDID information, nor do we request this directly from the display. We simply ask the system for the resolution of the connected displays, which is what you yourself have chosen in the system setup. Then we send out an image at that resolution to the monitor. This image consists of the composited layers and advanced output transformations you have applied. EDIDs do not enter in Resolume at all.
If the resolution received from the system has changed, Resolume tries to maintain the mapping as best as possible. We try to scale the mapping to the new resolution, so if your output transformations were made at 1920x1080, they should still align when you set the new resolution to 1280x720. Any changes here *will* be reflected in the numbers shown in the Advanced Output.
If the output resolution has not changed, and the slices still show their previous values and transformations in the Advanced Output preview, but the projector is showing something different than before, the problem could be in two places.
One is that the projector could be doing some auto-alignment function which is wreaking havoc with your mapping. This is easily checked by sending a test card image through a new, non-transformed slice. If parts of the test card are not showing up, your projector is biting you in the ass.
The other is that Resolume is doing some unexplained things *after* the modifications you have told it to make in the Advanced Output. The only way to properly check this is to have some sort of preview monitor connected, which has a duplicate of the signal sent to the projector.
Because a preview monitor is not always on hand, we hope that you can take some time to document this behaviour with screenshots of the advanced output before and after, and the mapping before and after. Hopefully we can get an indication of the problem that way. Needless to say, we have never come across this situation, nor have we heard of anyone experiencing this before this post. So we're dependent on your info to help us track down any possible issues.
We always recommend to first do a Save As... via the preset drop down before shutting down and disconnecting, so you can always recall the preset at any time. Pressing Save&Close can cause a loss of data when the config.xml file is corrupted or deleted.