This discussion will mainly apply to ATSC transponders in North America, but the same issues can be found in some satellite transponders.

By default, enigma2 will save channels based on the Transport Stream ID, or TSID. The FCC requires all high powered ATSC television stations to have an unique TSID, but this Does Not apply to Low Power ATSC stations. In Atlanta, Ga., there are several Low Power ATSC stations that have a TSID of 0000.

When an enigma2 receiver scans a transponder with a TSID of 0000, then those channels are saved , and are usable. When the second transponder is scanned that has a TSID of 0000, then the channels that were scanned on the first transponder are unusable, and the channels for the second transponder are usable. This situation may be repeated multiple times during a scan if several transponders have the same TSID. Shown below is the error that will be seen when trying to view the first set of channels after the second set of channels has been scanned.
[Only registered and activated users can see links. ]

There are two ways to fix the SID not found in Pat IF the error is due to two or more transponders having the same TSID.
(1) Manually edit the transponders that have the same TSID, making the TSID unique between them. Doing this requires manually editing the transponder in lamedb, and editing all the channels associated with that transponder. Background scanning will probably need to be disabled so your edits are not automatically overwritten. (Manual Edits is what I had to do when this problem was first discovered in ATSC)

(2) Set the receiver to Ignore DVB-x namespace sub network to No in the receiver. Default for these settings is Yes. This setting for DVB-C, DVB-T, and DVB-S may be found in the Customize menu of the receiver in PLi type images. (OE Alliance images may have different menus, but the settings will be the same.)
DVB-C and DVB-T can apply to ATSC channels in North America. DVB-S should apply to all satellite transponders, such as DVB-S, DVB-S2, DVB-S2X.

Here is a screencap that shows all of three of these settings changed to No, which is the way I normally run the enigma2 receiver. These settings have worked in all of my enigma2 receivers for years, but they may cause issues in other parts of the world.
[Only registered and activated users can see links. ]

More information about this may be found in the links.
[Only registered and activated users can see links. ]
[Only registered and activated users can see links. ]

Requiring a TSID for some and not others seems like a dumb thing to do. This gave me headaches a few years ago...
[Only registered and activated users can see links. ]

Note: Delete the effected channels and re-scan after changing the settings.