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David;The heat generation will deteriorate those copper connections and silicone cap.
I have had three fail in 22 years. All from excess heat.
If your electrics are in the upper orientation simply loosen the hose clamps and spin it.
All that heat will go into the block and not the electrics.

David;Great observation and thanks.
I was wrong to call it a “block heater”.

I was referring to a lower radiator hose heater and the silicone rubber cap that holds the 4 copper contacts for temperature switch and immersion heater. When that silicone cap is oriented to the top of that lower radiator hose it degrades from heat and always fails first.
Rotate the heater 180 degrees to reduce or eliminate the problem.

[spring might be fatiuged to the point that your streching will be a temp. fix, but it will give you the knowledge if that is the issue with the starter]

I also think the shaft that the solenoid plunger  forces forward to engage those high amperage contacts is not  quite long enough to keep it from cocking sideways and initiating the start sequence but not continuing that start sequence.
That also might explain the second problem of the starter running uncontrollably because that shaft is not returning to its original non start position because it is bound it its bore. Higher spring pressure corrects the problem by forcing it back into the non- start position.
Agreed that it is only a temporary fix.

For many months now my 6 year old gear reduction starter on my 254 Jinma has been inconsistent.
It has slowly increased its failure to stay engaged with the flywheel. It initially engages but then disengages. It averages about 6 start cycles before the pistons are in the right position to start because the starter disengages so often that the flywheel only turns 1/3 turns or less.

Also about twice a year this starter has a separate problem.
When initially trying to start the engine the starter stays in start position even with the key quickly disengaged. I have to jump off the tractor while the starter is turning over and stop it at the emergency knife switch controlling the ground post on my battery. Initially I suspected the contacts in the solenoid were welding themselves together and creating the problem so I unsolder the solenoid leads to dissect the copper contacts. To my amazement everything looked average. Very little wear and no burn spots were evident.
I notice the return spring on the contacts connected to the rod that is actuated by the solenoid plunger was collapsed so I expanded the spring by 1/4”. And I greased and chamfered the contact rod.
Upon reassembly the starter seems to work better but only time will tell as I feel I haven’t really analyzed the problem.

After 15 years my 2010 Tacoma Tire Pressure Monitor System batteries began to fail.
Instead of paying $400 for replacements including the TPMS code reader I decided to buy a Hakka soldering station and 4/3 volt battery replacements.
The original sensors have a plastic cover that is easily pried off with a screwdriver once the sensor is removed from the rim/tire.
Under the plastic cover is potting compound that encases the battery and radio frequency electronics and pressure monitor.
That soft potting compound must be excavated from the battery and electronics. I used a blunt plastic probe to gently erode the compound into tiny clumps. There are 2plastic clips holding the battery and the electronics is pinned on two plastic locating posts.
Once most of the compound is removed gently insert the plastic probe under the battery and lift it while spreading the clips holding it. It is soldered to the electronics circuit board so the board must also gently be lifted off the locating posts with that plastic pointer. Be very gentle as the are tubing on that Circuit board.
Once released from the case the remaining potting compound can be totally removed using the probe from around the two solder points on the circuit board holding the battery to the electronics. Use your DVM meter set on voltage to determine the correct Plus and minus polarity of the battery to the circuit board.
Use flux coated wicking copper braid to desolder the plus/minus connection of the battery. YouTube tutorials show how easy this is.
You can buy  the special high dollar F welded connectors that are welded to the new 3volt battery replacement but I used the copper braid to connect the new batteries to the circuit board. Just make sure the polarity is correct
Once the new battery is soldered in place and replaced in the sensor housing buy some 2 part liquid potting compound  and entomb it back into the housing  The compound takes 24 hours to cure. Silicone caulk is acidic and should not be used