I dont think this is a channel list problem. As the message says "scrambled" and not "unavailable" this seems to be related to the emu. Of course the shown message might be wrong - what does the reception details tell you about signal strengh and quality, or if available about errors/BER ?
what about a logfile from your emulator - BTW: what emulator do you use ?
RTE (as all Irish channels ?!) are decoded by CAID 0960, while SkyUK is decoded by CAID 0963. In addition, to make it complicated, RTE also serve CAID 0963 (but the CS-server does not decode RTE by CAID 0963).
So I believe the 1st time your emulator decode the channel successful it uses CAID 0960, when you switch the channel and switch back the emulator tries to use CAID 0963 onl and does not switch to CAID 0960 anymore. Most likely CAID 0963 is prioritized (what is correct for all Sky UK channels as the CS-server decode SkyUK by CAID 0963).
There are options to solve the problem, especially if you use Oscam I am sure this can be sorted out, but before writing unnecessary configurations you need to say what emu you use and if it is Oscam if it uses dvbapi-mode and what protocol (newcamd or cccam).
And as I said: a logfile would be fine :-)
BTW: I have no problems to decode RTE One, also if I switch to an unscambled or SkyUK channel it decodes RTE 1 again (after one unsuccessful try via CAID 0963 Oscam switches to CAID 0960 for successful decoding of the channel). Fine for me, as Oscam recognizes very fast that CAID 0963 will not decode the channel before switching to CAID 0960 but this could also be optimized (at least on Oscam). So it is for sure no server-problem.
Be carefull simply "trying something out without knowledge" at least for Oscam there are configuration options which might result in a vioation of server rules.