THE SSRMS is removing/replacing something on the ISS feed. An RPC?
Looking at the feed myself, it's an RPCM R&R that is in work. The view is from the SPDM looking at the alignment target of the RPCM.
Finally, Controllers maneuvered the SSRMS to the start position for the MBSU2 R&R which is scheduled on May 4.
ISS Robots Replace Critical Power Switching Box Outside Space StationSpaceflight101Published on 6 May 2017Details/Background: http://spaceflight101.com/expedition-51/iss-robots-begin-critical-mbsu-replacement/Time lapse video of the International Space Station's robots working May 4 through 6 to replace a partially failed Main Bus Switching Unit on the Station's S0 truss segment - a critical power distribution hub that conditions two of eight power channels available on ISS.Main Bus Switching Unit #2 (MBSU 2) exhibited a Loss Of Communications (LOC) failure on April 25, 2017 - no longer sending status telemetry and unable to be commanded from the ground, but still passing power to downstream uses. A similar fault occurred on MBSU #1 in 2011 and was believed to be radiation-related damage to the unit's Switchgear Controller Assembly. MBSU #1 was replaced in 2012 by spacewalking astronauts, but through growing confidence in the Station's robots, it was decided to have Dextre attempt the MBSU replacement. Prerequisites for the replacement were completed on May 4 and included the reconfiguration of the Station's power system to allow MBSU #2 to be powered off without affecting any critical systems. The two-armed Dextre, riding on the end of the 18-meter long Canadarm2, picked up the spare MBSU from External Stowage Platform 2 (ESP-2) on Thursday and stowed in on its Enhanced ORU Temporary Platform (EOTP) side 2. Starting Friday afternoon (UTC), Dextre began the actual replacement work, releasing the H1 secondary bolt from MBSU #2 before removing the 99-Kilogram unit by releasing the H2 primary bolt. Dextre then used its other arm to remove the spare from its Flight Releasable Attachment System (FRAM) on the EOTP before moving in position to install the spare. Guide rails helped with placing the spare unit, automatically connecting blind-mate electrical and data interfaces on the back of the MBSU. Two bolts were driven to secure the MBSU followed by dealing with the failed unit - first placing it into the empty FRAM on the EOTP and then moving it to a stowage location on ESP-2.Mission Controllers confirmed good health of the MBSU early on Saturday and began restoring the normal ISS power architecture, informing the crew that all would be back to normal by the end of the day. The video plays at 45x real speed, use YouTube's Speed Controls to further speed it up or slow it down. Views that appear pink in color are due to a faulty camera on the Station's Mobile Servicing System.