Tutorial 3 and map frame problems

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Hi,

After the last update of Ubuntu, I'm having a lot of problems with nav2d. I have downloaded nav2d and the other needed packages (rviz, stage_ros, joy, p2os) but, when I start tutorial 3 (without changing anything) with the command

roslaunch nav2d_tutorials tutorial3.launch

I get some problems. Everything seems fine (both stage and rviz are correctly opened and I can start the exploration without problems) until, in Rviz, the robot seems to start blocking and making little jumps after a couple of seconds. Then the exploration goes fine for a little time, but it then does the same behaviour again. This often leads to bad maps in Rviz, for example creating walls where there should be none, and eventually failing the exploration. Every time the robot begins blocking, both the Desired and Corrected operator topics in Rviz show this error message:

Transform [sender=unknown_publisher] For frame [odom]: No transform to fixed frame [map]. TF error: [Lookup would require extrapolation into the future. Requested time 169.800000000 but the latest data is at time 168.600000000, when looking up transform from frame [odom] to frame [map]]

While the topic LaserScan in Rviz shows this message:

Transform [sender=unknown_publisher] For frame [base_laser_link]: No transform to fixed frame [map]. TF error: [Lookup would require extrapolation into the future. Requested time 169.800000000 but the latest data is at time 168.600000000, when looking up transform from frame [base_laser_link] to frame [map]]

Sometimes after one of these blocks has gone on for some time, an error pops up in the command line:

[ERROR] [1539077791.154842789, 221.600000000]: Could not get robot position: Lookup would require extrapolation into the past. Requested time 211.400000000 but the earliest data is at time 211.600000000, when looking up transform from frame [base_link] to frame [map]

Here is an image of the screen in Rviz, hoping it can help in identifying the problem:

I tried looking at some other topics, but I haven't found a solution. I first had these problems when doing the same with my map and my exploration plugins, but after I created another catkin workspace and installing a fresh copy of all the packages, included nav2d, I found out that the problems remain the same. I also noticed these problems before the last package update, but they now happen every time, while before they only happened not very often and with little real effect. I'm using Kinetic on an Acer Aspire E15 with 4GB RAM. If you need any other information, please ask me and I'll try to do anything I can.

Thanks in advance for your help!